Fluid jet device, drive device of fluid jet device, surgical instrument, and method of driving fluid jet device

ABSTRACT

A fluid jet device including a fluid chamber with variable capacity and a capacity varying section adapted to vary the capacity of the fluid chamber in response to supply of a drive signal. A drive waveform section making the capacity varying section operate so as to compress the capacity of the fluid chamber and a restoring drive waveform section making the capacity varying section operate to restore the capacity of the fluid chamber before compressing the capacity in a signal waveform. The drive signal supply section controls supply content of the drive signal to provide a restoring period adapted to restore a steady state of the fluid flowing toward an inside of the fluid chamber in a period from when the compressing drive waveform section in the drive signal is supplied to when a subsequent compressing drive waveform section is supplied.

This is a Continuation of application Ser. No. 12/552,768 filed Sep. 2,2009, which claims the benefit of Japanese Application No. 2008-236106filed Sep. 16, 2008. The disclosure of the prior application is herebyincorporated by reference herein in its entirety.

BACKGROUND

1. Technical Field

The present invention relates to a fluid jet device for emitting a jetof a fluid at high speed, and in particular to a fluid jet devicesuitable for emitting a jet of a fluid in the condition of maintainingdesired jet force.

2. Related Art

In the past, as a fluid jet device for incising or excising body tissue,there is known a device provided with a pulsation generation sectionhaving a fluid chamber with a variable capacity, an entrance channel andexit channel communicated to the fluid chamber, and a capacity varyingsection for varying the capacity of the fluid camber in response tosupply of a drive signal, a connection channel having one endcommunicated to the exit channel and the other end provided with a fluidjet opening section (a nozzle) with a diameter smaller than that of theexit channel, a connection channel tube provided with the connectionchannel penetrating therethrough and having rigidity with which thepulsation of the fluid flowing from the fluid chamber can be transmittedto the fluid jet opening section, and a pressure generation section forsupplying the entrance channel with the fluid, and for supplying theentrance channel with the fluid with the pressure generation section ata constant pressure, and at the same time varying the capacity of thefluid chamber with the capacity varying section to generate thepulsation, thereby performing ejection operation of the fluid (e.g.,JP-A-2008-82202 (Document 1)).

According to the Document 1, a patent application by the inventors ofthe invention, in the case in which the capacity of the fluid chamber ofa fluid jet device is not varied, the fluid flows through the fluidchamber in the condition in which the supply pressure by the pressuregeneration section (e.g., a pump) and the channel resistance balancedwith each other. When shrinking the fluid chamber rapidly, the pressurein the fluid chamber rises. At that moment, since an increased amount offluid ejected from the exit channel is larger than a decreased amount offlow volume of the fluid flowing from the entrance channel into thefluid chamber, a pulsation flow occurs in the connection channel. Thepressure pulsation in the ejection operation propagates in theconnection channel tube, and thus the fluid jet is emitted from thefluid jet opening section of the nozzle at the tip of the connectionchannel tube. The fluid chamber becomes in a vacuum state (0 atm ornearly 0 atm) immediately after the pressure rise due to the interactionbetween decrease in inflow volume of the fluid from the entrance channeland increase in outflow of the fluid from the exit channel. As a result,after predetermined time has elapsed due to both of the pressure of thepump and the vacuum state inside the fluid chamber, there is restoredthe flow of the fluid in the entrance channel towards the inside of thefluid chamber at the same speed as before the operation of thepiezoelectric element.

In the technology of the related art described in the Document 1,although it is arranged that the capacity varying section configuredincluding the piezoelectric element and a diaphragm is driven by apulsed drive signal, in the case, for example, in which it is driven bya simple sinusoidal drive signal, the subsequent capacity reductionoperation (compressing operation) might be performed before the flowproceeding toward the inside of the fluid chamber is restored to thesteady state. If the subsequent compressing operation is performedbefore restoring the steady state, it is not achievable to obtainsufficiently strong jet force (jet).

SUMMARY

An advantage of some aspects of the invention is to provide a fluid jetdevice, a drive device for the fluid jet device, a surgical instrument,and a driving method of the fluid jet device, each suitable forcontinuously emitting jet of the pulsation flow in the condition ofmaintaining desired jet force.

A first aspect of the invention is directed to a fluid jet deviceincluding a fluid chamber with a variable capacity, an entrance channelcommunicated with the fluid chamber, an exit channel communicated withthe fluid chamber, a capacity varying section adapted to vary thecapacity of the fluid chamber in response to supply of a drive signal,an opening section communicated with a different end of the exit channelfrom an end of the exit channel with which the exit channel iscommunicated with the fluid chamber, a pressure generation sectionadapted to supply the entrance channel with a fluid, and a drive signalsupply section adapted to supply the capacity varying section with adrive signal including a compressing drive waveform section making thecapacity varying section operate so as to compress the capacity of thefluid chamber and a restoring drive waveform section making the capacityvarying section operate so as to restore the capacity of the fluidchamber before compressing the capacity in a signal waveform of onecycle, and the drive signal supply section controls supply content ofthe drive signal so as to provide a restoring period adapted to restorea steady state of the fluid flowing toward an inside of the fluidchamber in a period from when the compressing drive waveform section inthe drive signal is supplied to the capacity varying section to when asubsequent one of the compressing drive waveform section is supplied tothe capacity varying section.

According to the configuration described above, when the drive signalsupply section supplies the capacity varying section with thecompressing drive waveform section in the drive signal, the capacityvarying section acts to compress the capacity of the fluid chamber, andthus the inside of the fluid chamber is compressed. Then, when thesupply of the compressing drive waveform section is terminated, therestoring drive waveform section in the drive signal is then supplied tothe capacity varying section. Thus, the capacity varying section acts inthe direction of restoring the capacity of the fluid chamber to thestate prior to the compression, thereby restoring the inside of thefluid chamber, which is now in the compressed state. Further, the drivesignal supply section controls the supply content of the drive signal sothat the restoring period for restoring the flow of the fluid toward thefluid chamber to be in the steady state is provided in a period from theend of supply of the compressing drive waveform section to the supply ofthe subsequent compressing drive waveform section.

In other words, when the drive signal supply section terminates thesupply of the previous compressing drive waveform section to thecapacity varying section, it is possible to restore the steady state(the state in which the fluid is flowing while the supply pressure fromthe pressure generation section and the flow resistance are balancedwith each other) in the fluid chamber prior to the supply of thesubsequent compressing drive waveform section.

Thus, since it becomes possible to make the capacity varying sectionperform the subsequent compressing operation after the flow of the fluidtoward the fluid chamber is restored to be the steady state, it ispossible to obtain an advantage that emission of the fluid jet cancontinuously be performed while keeping the jet force in a constant andstrong state.

Here, the expression “to be communicated with” means that one thing andthe other thing are connected to each other, no matter whether directlyor indirectly, so that a fluid can flow therethrough. For example, thecondition in which an end of the exit channel and the fluid jet openingsection are connected to each other directly or via a channel tube orthe like so that the fluid can flow therethrough corresponds to theexpression.

Further, a second aspect of the invention is directed to the fluid jetdevice of the first aspect of the invention, wherein a time length ofthe compressing drive waveform section is denoted as T_(red), a timelength of the restoring drive waveform section is denoted as T_(exp),average pressure in the fluid chamber in a supply period of thecompressing drive waveform section is denoted as P_(gen), pressureapplied to the entrance channel in the fluid chamber on a pressuregeneration section side in a supply period of the restoring drivewaveform section is denoted as P_(sup), and the drive signal supplysection supplies the capacity varying section with the drive signalconfigured including the compressing drive waveform section with thetime length T_(red) and the restoring drive waveform section with thetime length T_(exp) satisfying a relationship of a following formula.T _(red)×(P _(gen) −P _(sup))≦T _(exp) ×P _(sup)

Here, denoting the cross section of the entrance channel as s, themomentum M_(g) acting on the entrance channel on the fluid chamber sideis expressed as M_(g)=s×T_(red)×(P_(gen)−P_(sup)), and the momentumM_(s) acting on the entrance channel on the pressure generation sectionside is expressed as M_(s)=s×T_(exp)×P_(sup). Further, in general,P_(sup) takes a far smaller value compared to P_(gen)(P_(gen)>>P_(sup)).

Further, in a period (the period of T_(exp)) during which the capacityof the fluid chamber is expanding (restoring the original capacity), theaverage pressure of the fluid chamber becomes 0 atm or nearly 0 atmbecause the fluid is drawn due to the inertance of the exit channel. Inother words, if the momentum M_(s) provided thereto in T_(exp) is equalto or larger than the momentum M_(g) provided thereto in T_(red), thefluid can be restored to the original steady state.

Therefore, in the case of the configuration described above, since it ispossible to supply the capacity varying section with the drive signalhaving the compressing drive waveform section with the time lengthT_(red) and the restoring drive waveform section with the time lengthT_(exp) satisfying the relationship of the formula described above, thefluid can be restored from the vacuum state to the original steady statein one cycle period of the drive signal.

Thus, since it becomes possible to make the capacity varying sectionperform the subsequent compressing operation after the flow of the fluidtoward the fluid chamber is restored to be the steady state, it ispossible to obtain an advantage that emission of the fluid jet cancontinuously be performed while keeping the jet force in a strong state.

Further, it might be possible, for example, that a signal is raisedrapidly and then dropped rapidly as the burst waveform shown in FIG. 16,and then, waiting for the flow toward the fluid chamber to be restoredbefore supplying the subsequent signal.

However, in this case, since the inside of the fluid chamber expands(restores the original capacity) rapidly, the vacuum bubbles in thefluid chamber also expand, and the gases solved in the fluid become aptto be discharged toward the vacuum bubbles. As a result, although theflow to the fluid chamber is restored and the vacuum bubbles disappear,since the bubbles caused by the gases once discharged from the liquidnever disappear, the bubbles lower the rigidity of the fluid chamber,and as a result, the rise in pressure might be prevented to make theemission of the fluid jet weaker.

According to the configuration described above, since the drive signalsatisfying the relationship of the formula described above can besupplied to the capacity varying section, P_(gen)>>P_(sup) is satisfied,and therefore, T_(exp) becomes a longer time length than T_(red), and asa result, the capacity of the fluid chamber thus compressed is restoredto the original state relatively slowly, and as a result, the vacuumbubbles become smaller, and it becomes possible to make it difficult todischarge the gases from the fluid to the vacuum bubbles.

Thus, the advantage that the rigidity of the fluid chamber can beprevented from dropping due to the bubbles of the gases can also beobtained.

Further, a third aspect of the invention is directed to the fluid jetdevice of the first or the second aspect of the invention, wherein thedrive signal supply section controls the supply content of the drivesignal so as to provide the restoring period in the supply period of therestoring drive waveform section.

According to the configuration described above, in a period of one cycleof the drive signal, it is possible to perform compression of thecapacity of the fluid chamber, restoring to the original capacity, andrestoring of the flow of the fluid toward the fluid chamber to thesteady state. Thus, since it becomes possible to make the capacityvarying section perform the subsequent compressing operation after theflow of the fluid toward the fluid chamber is restored to be the steadystate, it is possible to obtain an advantage that emission of the fluidjet can continuously be performed while keeping the jet force in astrong state.

Further, a fourth aspect of the invention is directed to the fluid jetdevice of the third aspect of the invention, wherein the drive signalsupply section supplies the capacity varying section with the drivesignal having a constant waveform section holding a constant signallevel as the restoring period between the compressing drive waveformsection and the restoring drive waveform section and in a part of therestoring drive waveform section.

According to the configuration described above, it is possible tooperate the capacity varying section so as to keep (stop varying thecapacity) the capacity of the fluid chamber constant for a predeterminedtime period after compressing the capacity of the fluid chamber as arestoring period.

Thus, since the vacuum bubbles can be made to disappear in the state inwhich the capacity is compressed and the capacity is not substantiallyvaried, an advantage of making the vacuum bubbles disappear in a shortperiod of time can be obtained.

Further, since it is also possible to restore the capacity after thevacuum bubbles disappear or roughly disappear, an advantage that thedischarge of the gases from the fluid can be prevented can also beobtained.

Further, a fifth aspect of the invention is directed to either one ofthe fluid jet device of the first through fourth aspects of theinvention, wherein a storage section adapted to store waveforminformation of the drive signal is additionally provided, the drivesignal supply section generates the drive signal based on the waveforminformation stored in the waveform information storage section, andsupplies the capacity varying section with the drive signal.

According to the configuration described above, for example, by storingthe waveform data sampled at a predetermined cycle as the waveforminformation, it is possible to easily generate the drive signal of thetarget waveform from the waveform data.

Further, a sixth aspect of the invention is directed to the fluid jetdevice of either one of the first through fifth aspects of theinvention, wherein the drive signal supply section supplies the capacityvarying section with the drive signal having the signal waveform of onecycle configured by combining a part of a sine wave, which forms thecompressing drive waveform section, and a time length of one cycle ofwhich is T1, and a part of a sine wave, which forms the restoring drivewaveform section, and a time length of one cycle of which is T2 (T1≠T2).

According to the configuration described above, since it is possible toconfigure the drive signal by combining a part of one sine wave and apart of another sine wave, the time length of one cycle of the one sinewave and the time length of one cycle of the another sine wave beingdifferent from each other, denoting, for example, the wavelength of thesine wave of T1 as λ1, the wavelength of the sine wave of T2 as λ2, thedrive signal can be configured by combining a waveform portioncorresponding to the anterior half λ1/2 of the sine wave of T1 and awaveform portion corresponding to the posterior half λ2/2 of the sinewave of T2.

Thus, there is obtained an advantage that the drive signal, which hasthe time length of the posterior half cycle longer then the time lengthof the anterior half cycle, and at the same time, which has the signalwaveform of one cycle different from a simple sine wave, can easily beconfigured. In other words, the drive signal including the restoringperiod in the restoring drive waveform section can easily be configured.

Further, a seventh aspect of the invention is directed to the fluid jetdevice of the fifth aspect of the invention, wherein a shape of atrapezoidal wave is adopted as the signal waveform of one cycle.

According to the configuration described above, since the drive signal(analog signal) can be generated from the waveform data of a smallernumber of samples compared to the case with the sine wave signals, thedata capacity of the waveform data stored in the waveform informationstorage section can be reduced.

Thus, there can be obtained an advantage that the storage capacity ofthe waveform information storage section can be made smaller compared tothe case of using the sine wave signal as the drive signal, and at thesame time, there can also be obtained an advantage that a larger numberof types of waveform data can be stored in the waveform informationstorage section with the same capacity compared to the case in which thesine wave signal is used as the drive signal.

Further, an eighth aspect of the invention is directed to the fluid jetdevice of the seventh aspect of the invention, wherein the storagesection stores nodal point information of the trapezoidal wave as thewaveform information, and the drive signal supply section generates thedrive signal of the trapezoidal wave based on the nodal pointinformation stored in the storage section.

According to the configuration described above, by storing only thenodal point information of each of the trapezoidal waves as the waveforminformation it is possible to generate the desired drive signal from thewaveform information, and therefore, it is possible to reduce thewaveform information to be stored in the storage section to a smalleramount of data.

Further, in the case in which real-time access is required to generatethe drive signal, it is enough to read out a smaller amount of datacompared to the case of using the sine wave signal as the drive signal,and therefore, such a high-speed access mechanism required for the caseof using the sine wave signal as the drive signal is not required.

Therefore, there can be obtained an advantage that the drive controlusing the waveform information with various wavelengths and amplitudescan be realized at lower cost compared to the case of using the sinewave signal as the drive signal.

Further, a ninth aspect of the invention is directed to the fluid jetdevice of either one of the first through eighth aspects of theinvention, wherein a diameter of an end of the exit channel on a fluidchamber side is set to be larger than a diameter of an end of the exitchannel on an opening section side.

According to the configuration described above, there can be obtained anadvantage that the fluid flowing from the fluid chamber side end of theexit channel can be emitted in the opening section side end of the exitchannel as a pulsed droplet with higher pressure and higher speed.

Further, a tenth aspect of the invention is directed to the fluid jetdevice of either one of the first through ninth aspects of theinvention, wherein an inertance of the entrance channel is set to belarger than an inertance of the exit channel.

According to the configuration described above, when driving thecapacity varying section to compress the capacity of the fluid chamber,a larger pulsation flow than the inflow amount of the fluid from theentrance channel to the fluid chamber occurs in the exit channel, thusthe pulsed fluid ejection can be performed in the connection channeltube.

Further, an eleventh aspect of the invention is directed to the fluidjet device of either one of the first through ninth aspects of theinvention, wherein a combined inertance on an upstream side of the fluidchamber including the entrance channel is larger than an inertance on adownstream side of the fluid chamber including the exit channel.

According to the configuration described above, when driving thecapacity varying section to compress the capacity of the fluid chamber,a larger pulsation flow than the inflow amount of the fluid from theentrance channel to the fluid chamber occurs in the exit channel, thusthe pulsed fluid ejection can be performed in the connection channeltube.

Further, a twelfth aspect of the invention is directed to the fluid jetdevice of either one of the first through eleventh aspects of theinvention, wherein there are further provided a connection channelhaving a first end communicated with the exit channel, and a second endprovided with the opening section having a diameter smaller than adiameter of the exit channel, and a connection channel tube throughwhich the connection channel penetrates, and which transmits pulsationof the fluid flowing from the fluid chamber to the opening section.

According to the configuration described above, it becomes possible tomore strongly emit a jet of the fluid, and at the same time, in the casein which the fluid jet device according to this aspect of the inventionis used, for example, as a surgical instrument, it becomes applicable tovarious operations such as an operation on the brain in which theaffected area is located in a recess.

Further, a thirteenth aspect of the invention is directed to the fluidjet device of either one of the first through twelfth aspects of theinvention, wherein the capacity varying section is configured includinga diaphragm adapted to seal an end of the fluid chamber, and apiezoelectric element having one end fixed to the diaphragm and one ofexpanding and shrinking in a direction perpendicular to a seal surfacein response to supply of the drive signal, and the drive signal supplysection makes the piezoelectric element expand to deform the diaphragmtoward an inside of the fluid chamber by supplying the compressing drivewaveform section in the drive signal, and makes the piezoelectricelement shrink to restore the diaphragm in a deformed state to thediaphragm in a state prior to the deformation by supplying the restoringdrive waveform section in the drive signal.

According to the configuration described above, since the piezoelectricelement is adopted as the capacity varying section, there can beobtained an advantage that the capacity variation of the fluid chambercan easily be controlled by the drive signal, and at the same time,there can also be obtained an advantage that the simplification of thestructure and associated downsizing can be realized. Further, since itis possible to set the highest frequency of the capacity variation ofthe fluid chamber to be a high frequency equal to or higher than, forexample, 1 kHz, there can be obtained an advantage that the emission ofa jet of the pulsation flow can be executed at high speed and with ashort cycle period.

Meanwhile, a fourteenth aspect of the invention is directed to a drivedevice of a fluid jet device including a fluid chamber with a variablecapacity, an entrance channel and an exit channel each communicated withthe fluid channel, a capacity varying section adapted to vary a capacityof the fluid chamber in response to supply of a drive signal, an openingsection communicated with a different end of the exit channel from anend of the exit channel communicated with the fluid chamber, a pressuregeneration section adapted to supply the entrance channel with a fluid,and a drive signal supply section adapted to supply the capacity varyingsection with a drive signal including a compressing drive waveformsection making the capacity varying section operate so as to compressthe capacity of the fluid chamber and a restoring drive waveform sectionmaking the capacity varying section operate so as to restore thecapacity of the fluid chamber before compressing the capacity in asignal waveform of one cycle, and the drive signal supply sectioncontrols supply content of the drive signal so as to provide a restoringperiod adapted to restore a steady state of the fluid flowing toward aninside of the fluid chamber in a period from when the compressing drivewaveform section in the drive signal is supplied to the capacity varyingsection to when a subsequent one of the compressing drive waveformsection is supplied to the capacity varying section.

According to the configuration described above, substantially the samefunctions and advantages as of the fluid jet device according to thefirst aspect of the invention can be obtained.

Further, a fifteenth aspect of the invention is directed to a surgicalinstrument adapted to assist a therapeutic treatment of an affected areaby fluid jet emission, including the fluid jet device according toeither one of the first through thirteenth aspects of the invention.

According to the configuration described above, it is possible toperform assistance of a therapeutic treatment such as excision of anaffected area such as a tumor using a fluid jet emission by the fluidjet device according to either one of the first through thirteenthaspects of the invention.

Further, a sixteenth aspect of the invention is directed to a method ofdriving a fluid jet device including the steps of (a) providing a fluidchamber with a variable capacity, an entrance channel and an exitchannel each communicated with the fluid chamber, a capacity varyingsection adapted to vary a capacity of the fluid chamber in response tosupply of a drive signal, an opening section communicated with adifferent end of the exit channel from an end of the exit channelcommunicated with the fluid chamber, a pressure generation sectionadapted to supply the entrance channel with a fluid, and a drive signalsupply section, and (b) making the drive signal supply section supplythe capacity varying section with a drive signal including a compressingdrive waveform section making the capacity varying section operate so asto compress the capacity of the fluid chamber and a restoring drivewaveform section making the capacity varying section operate so as torestore the capacity of the fluid chamber before compressing thecapacity in a signal waveform of one cycle, and in step (b), the drivesignal supply section is made to control supply content of the drivesignal so as to provide a restoring period adapted to restore a steadystate of the fluid flowing toward an inside of the fluid chamber in aperiod from when the compressing drive waveform section in the drivesignal is supplied to the capacity varying section to when a subsequentone of the compressing drive waveform section is supplied to thecapacity varying section.

According to the configuration described above, substantially the samefunctions and advantages as of the fluid jet device according to thefirst aspect of the invention can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is an explanatory diagram showing a schematic configuration of afluid jet device according to the present embodiment of the invention.

FIG. 2 is a cross-sectional view showing a structure of a pulsationgeneration section according to the embodiment of the invention.

FIG. 3 is an exploded diagram of a fluid jet emitting section.

FIG. 4 is a plan view showing a form of an entrance channel.

FIG. 5 is a block diagram showing a detailed configuration of a drivesection.

FIG. 6 is a flowchart showing a process of generating a signal waveformin the drive section.

FIG. 7 is a flowchart showing a process of supplying the pulsationgeneration section with a drive signal in the drive section.

FIG. 8 is a diagram showing an example of the signal waveform generatedby combining two types of sine waves.

FIG. 9A is a diagram showing an example of a method of expanding awaveform, and FIG. 9B is a diagram showing an example of a signalwaveform of a drive signal according to a second embodiment.

FIG. 10 is a block diagram showing a detailed configuration of a drivesignal supply section according to a third embodiment.

FIG. 11 is a diagram showing an example of a trapezoidal wave formingthe drive signal.

FIG. 12 is a flowchart showing a process of outputting the drive signalin a drive signal supply process of the third embodiment.

FIG. 13 is a flowchart showing a counter condition setting processcorresponding to the steps S308 and S324.

FIG. 14 is a diagram showing an example of waveform information of thethird embodiment.

FIG. 15 is a diagram showing an output example of a drive signal of atrapezoidal wave.

FIG. 16 is a diagram showing an example of a drive signal having a burstwave for driving the piezoelectric element.

DESCRIPTION OF EXEMPLARY EMBODIMENTS First Embodiment

A first embodiment of the invention will hereinafter be explained withreference to the accompanying drawings. FIGS. 1 through 8 are diagramsshowing a fluid jet device, a drive device of the fluid jet device, asurgical instrument, and a method of driving the fluid jet deviceaccording to the first embodiment of the invention.

It should be noted that the fluid jet device according to the embodimentof the invention can be adopted for various purposes such as drawingwith ink or the like, cleaning a fine object and a structure, ablationor excision of an object, and a surgical knife, and in the embodimentexplained hereinafter, the explanations are presented exemplifying thefluid jet device suitable for incising or excising body tissue.Therefore, the fluid used in the embodiment is water, saline, medicalsolution, or the like.

Firstly, a configuration of the fluid jet device according to theembodiment of the invention will be explained with reference to FIG. 1.FIG. 1 is an explanatory diagram showing a schematic configuration ofthe fluid jet device 1 according to the present embodiment of theinvention.

As shown in FIG. 1, the fluid jet device 1 is configured including, as abasic configuration, a fluid jet emitting section 2 configured includinga fluid container 10 for containing the fluid, a pump 20 as a pressuregeneration section, and a pulsation generation section 100 for making apulsing flow of the fluid supplied from the pump 20, and a drive section30 for driving the pulsation generation section 100.

A connection channel tube 200 with a thin pipy shape is connected to thepulsation generation section 100, and a tip portion of the connectionchannel tube 200 is provided with a nozzle 211 with a shrunk channelinserted therein.

Then, the flow of the fluid in the fluid jet device 1 will briefly beexplained with reference to FIGS. 1 and 2.

Here, FIG. 2 is a cross-sectional view showing a structure of thepulsation generation section 100 according to the embodiment of theinvention. It should be noted that the lateral direction in FIG. 2corresponds to the vertical direction. Further, FIG. 2 is across-sectional diagram along the A-A′ line shown in FIG. 3 describedlater.

The fluid contained in the fluid container 10 is suctioned by the pump20 via a connection tube 15, and supplied to the pulsation generationsection 100 at constant pressure via a connection tube 25. The pulsationgeneration section 100 is provided with a fluid chamber 501, and acapacity varying section for varying the capacity of the fluid chamber501 in accordance with a drive signal from the drive section 30, anddriving the capacity varying section to generate pulsation, therebyemitting a jet of fluid at high speed through a connection channel tube200 and a nozzle 211. Detailed explanations of the pulsation generationsection 100 will be described later.

It should be noted that, when performing an operation using the fluidjet device 1, the region the operator grips is the pulsation generationsection 100. Therefore, it is preferable that the connection tube 25 tothe pulsation generation section 100 is as flexible as possible. Inorder for achieving the above, it is preferable to apply the lowestpossible pressure to the fluid in a range in which the fluid can be sentto the pulsation generation section 100 using a flexible tube with athin wall.

Further, in particular in the case such as an operation on the brain, inwhich a failure in the device might cause a significant accident, it isnecessary to prevent a high-pressure fluid from spouting in response tobreak of the connection tube 25, and in view of this point, it isrequired to keep the fluid at low pressure.

Hereinafter, a structure of the pulsation generation section 100 will beexplained with reference to FIGS. 2 through 4.

Here, FIG. 3 is an exploded view of the fluid jet emitting section 2,and FIG. 4 is a plan view showing a form of an entrance channel 503, andshows an appearance of an upper case 500 viewed from a bonded surfaceside between the upper case 500 and a lower case 301.

As shown in FIGS. 2 through 4, the pulsation generation section 100 isprovided with the upper case 500 with threaded holes 500 a opened on thefour corners thereof, and the lower case 301 with threaded holes 301 a(not shown) opened on the four corners thereof. Further, the upper case500 and the lower case 301 are bonded on the surfaces thereof opposed toeach other so that the threaded holes 500 a and the threaded holes 301 aare opposed respectively to each other, and four screws 600 (not shown)are screwed in the threaded holes 500 a and 301 a, thereby screwing theupper case 500 and the lower case 301 to each other.

The lower case 301 is a hollow cylinder-shaped member having a brimsection, and one end thereof is sealed with a bottom plate 311. In theinternal space of the lower case 301, there is disposed a piezoelectricelement 401 as one of the members forming the capacity varying section.

The piezoelectric element 401 is a stacked piezoelectric element, andforms an actuator. One end of the piezoelectric element 401 is fixed toa diaphragm 400 via an upper plate 411, and the other end thereof isfixed to an upper surface 312 of the bottom plate 311.

Further, the diaphragm 400 is formed of a disc-like metal thin plate,and has a peripheral portion adhering and fixed to a bottom surface of aring-like concave section 303 provided to the upper surface side of thelower case 301 within the concave section 303. On the upper surface ofthe diaphragm 400, there is disposed, in a stacked manner, a reinforcingplate 410 formed of a disk-like metal thin plate having a circularopening section at the center thereof.

According to this configuration, by the drive section 30 inputting adrive signal to the piezoelectric element 401, the piezoelectric element401 expands or shrinks, and the upward force caused by the expansion andthe downward force caused by the shrinkage move the upper plate 411 inup-and-down directions. Then, the movement of the upper plate 411deforms the diaphragm 400, thereby varying the capacity of the fluidchamber 501.

In other words, the capacity varying section is composed of thepiezoelectric element 401, the upper plate 411, the diaphragm 400, andthe reinforcing plate 410.

The upper case 500 has a circular concave section formed at the centralsection of the surface thereof opposed to the lower case 301, and asolid of revolution composed of the concave section and the diaphragm400 and filled with a fluid is defined as the fluid chamber 501. Inother words, the fluid chamber 501 is defined as a space surrounded by aseal surface 505 of the concave section of the upper case 500, innercircumferential wall 501 a, and the diaphragm 400. At a substantiallycentral section of the fluid chamber 501, there is bored an exit channel511.

The exit channel 511 penetrates from the fluid chamber 501 to an end ofan exit channel tube 510 disposed so as to protrude from one end surfaceof the upper case 500. A connection section of the exit channel 511 withthe seal surface 505 of the fluid chamber 501 is smoothly rounded inorder for reducing the fluid resistance.

It should be noted that although the shape of the fluid chamber 501described hereinabove is a substantially cylindrical shape sealed at theboth ends, this is not a limitation, but the shape can be a conicalshape, a trapezoidal shape, or a hemispherical shape in the side view.For example, by adopting a funnel-like shape as the connection sectionof the exit channel 511 with the seal surface 505, it becomes easier todischarge bubbles in the fluid chamber 501 described later.

A connection channel tube 200 is connected to the exit channel tube 510.The connection channel tube 200 is provided with a connection channel201 penetrating therethrough, and the diameter of the connection channel201 is larger than the diameter of the exit channel 511. Further, thetube wall of the connection channel tube 200 is formed to have athickness in a range of providing rigidity not absorbing the pressurepulsation of the fluid.

A nozzle 211 is inserted in the tip portion of the connection channeltube 200. The nozzle 211 is provided with a fluid jet opening section212 penetrating therethrough. The diameter of the fluid jet openingsection 212 is smaller than the diameter of the connection channel 201.

On a side surface of the upper case 500, there is disposed an entrancechannel tube 502 so as to protrude therefrom, the entrance channel tube502 being inserted into the connection tube 25 for supplying the fluidfrom the pump 20, and provided with an entrance channel side connectionchannel 504 penetrating therethrough. The connection channel 504 iscommunicated with the entrance channel 503. The entrance channel 503 isformed on the peripheral portion of the seal surface 505 of the fluidchamber 501 to have a groove shape, and is communicated with the fluidchamber 501.

On the bonded surface between the upper case 500 and the lower case 301at a position apart from the outer circumference of the diaphragm 400,there are formed a gasket groove 304 on the lower case 301 side and agasket groove 506 on the upper case 500 side, and in the space formed bythe gasket grooves 304, 506, there is mounted a ring-like gasket 450.

Here, when assembling the upper case 500 and the lower case 301together, a peripheral portion of the diaphragm 400 and a peripheralportion of the reinforcing plate 410 have close contact with each otherby the peripheral portion of the seal surface 505 of the upper case 500and the bottom surface of the concave section 303 of the lower case 301.On this occasion, the gasket 450 is pressurized by the upper case 500and the lower case 301 to prevent leakage of the fluid from the fluidchamber 501.

The inside of the fluid chamber 501 becomes in a high-pressure state of,for example, 30 atm (3 MPa) or higher when ejecting the fluid, andalthough it is possible that the fluid slightly leaks at each of thebonding sections between the diaphragm 400, the reinforcing plate 410,the upper case 500, and the lower case 301, the gasket 450 prevents theleakage.

When disposing the gasket 450 as shown in FIG. 2, the gasket 450 iscompressed by the pressure of the fluid leaking from the fluid chamber501 at high pressure, and is further firmly pressed against inside wallsof the gasket grooves 304, 506, and therefore, the leakage of the fluidcan more reliably be prevented. Accordingly, the high-rate of pressurerise in the fluid chamber 501 can be maintained when driving.

Subsequently, the entrance channel 503 provided to the upper case 500will be explained in greater detail.

As shown in FIG. 4, the entrance channel 503 is formed by a grooveprovided to the peripheral portion of the seal surface 505 of the uppercase 500 and the reinforcing plate 410 pressed against and fixed to theseal surface 505.

The entrance channel 503 is communicated with the fluid chamber 501 atone end thereof, and is communicated with the connection channel 504 atthe other end thereof. At a connection section between the entrancechannel 503 and the connection channel 504, there is formed a fluidreservoir 507. Further, a connection section between the fluid reservoir507 and the entrance channel 503 is smoothly rounded, thereby reducingthe fluid resistance.

Further, the entrance channel 503 is communicated with the fluid chamber501 toward a substantially tangential direction with respect to theinner circumferential sidewall 501 a of the fluid chamber 501. The fluidsupplied from the pump 20 at constant pressure flows along the innercircumferential sidewall 501 a (in the direction indicated by the arrowin the drawing) to generate a swirling flow in the fluid chamber 501.Due to the centrifugal force of the swirling flow, the bubbles with alow density contained in the fluid chamber 501 are gathered at thecentral portion of the swirling flow.

Then, the bubbles thus gathered at the central portion are dischargedfrom the exit channel 511. Therefore, it is more preferable for the exitchannel 511 to be disposed near the center of the swirling flow, namelyat the axially central portion of the solid of revolution. In theexample shown in FIG. 4, the entrance channel 503 is curved to have aspiral planar shape. Although it is possible for the entrance channel503 to be communicated with the fluid chamber 501 with a straight line,it is curved because it is required to increase the channel length ofthe entrance channel 503 in order for obtaining a desired inertance in asmall space.

It should be noted that as shown in FIG. 2, the reinforcing plate 410 isdisposed between the diaphragm 400 and the peripheral portion of theseal surface 505 where the entrance channel 503 is formed. The purposefor providing the reinforcing plate 410 is to enhance durability of thediaphragm 400. Since a notch-like connection opening section 509 isprovided to the connection section of the entrance channel 503 with thefluid chamber 501, it is conceivable that stress concentration is causedin the vicinity of the connection opening section 509 when the diaphragm400 is driven at a high frequency, thereby causing fatigue breakdown.Therefore, it is arranged that the stress concentration can be preventedfrom occurring in the diaphragm 400 by disposing the reinforcing plate410 having a continuous opening section without a notch section.

Further, although in the fluid jet emitting section 2 explainedhereinabove, it is arranged that the four threaded holes 500 a are boredat outer peripheral portion of the upper case 500, and the upper case500 and the lower case 301 are screwed at the threaded holes, theconfiguration of the fluid jet emitting section 2 is not limitedthereto. For example, although omitted from the drawing, it is possibleto bond the reinforcing plate 410 and the diaphragm 400 with each other,thereby stacking and fixing them integrally to each other. As a fixingmethod, it is possible to adopt sticking with an adhesive, solid-phasediffusion bonding, welding, and so on, and it is further preferable thatthe reinforcing plate 410 and the diaphragm 400 adhere to each other inthe bonded surface.

Further, although in the fluid jet emitting section 2 describedhereinabove, there is adopted a configuration of connecting the exitchannel 511 and the nozzle 211 via the connection channel tube 200, theconfiguration is not limited thereto, and it is also possible to insertthe nozzle 211 in an end of the exit channel 511 on the opposite side tothe fluid chamber 501 without using the connection channel tube 200. Onthis occasion, a more simple configuration becomes possible.

Further, when used in an operation, it is more preferable to adopt aconfiguration of using the connection channel tube 200 to obtain alonger distance between a handpiece and a fluid jet ejection port.

Then, fluid ejection of the pulsation generation section 100 accordingto the present embodiment is performed by a difference between theinertance L1 (also referred to as a combined inertance L1 in some cases)on the entrance channel side and the inertance L2 (also referred to as acombined inertance L2 in some cases) on the exit channel side.

Firstly, the inertance will be explained.

The inertance L is expressed as L=ρ×h/S assuming that ρ denotes thedensity of the fluid, S denotes the cross section of the channel, and hdenotes the length of the channel. When assuming that the pressuredifference of the channel is ΔP, and the flow rate of the fluid flowingthrough the channel is Q, by transforming the motion equation in thechannel using the inertance L, the relationship of ΔP=L×dQ/dt isderived.

In other words, the inertance L represents the degree of the influenceexerted on the time variation of the flow rate, and the larger theinertance L is, the smaller the time variation of the flow rate is, andthe smaller the inertance L is, the larger the time variation of theflow rate is.

Further, a combined inertance with respect to a parallel connection of aplurality of channels or a series connection of a plurality of channelswith shapes different from each other can be calculated by combining theinertances of the respective channels in substantially the same manneras the parallel connection or the series connection of inductances in anelectrical circuit.

It should be noted that regarding the inertance L1 on the entrancechannel side, since the connection channel 504 is set to have a diametersufficiently larger than that of the entrance channel 503, the inertanceL1 can be obtained by calculating only the inertance of the entrancechannel 503. Further, the connection tube for connecting the pump 20 andthe entrance channel has flexibility, and therefore, is omitted from thecalculation of the inertance L1.

Further, regarding the inertance L2 on the exit channel side, in thecase in which the diameter of the connection channel 201 is far largerthan that of the exit channel, and the thickness of the tube portion(tube wall) of the connection channel tube 200 is small, the influenceon the inertance L2 is minimal. Therefore, the inertance L2 on the exitchannel side can be replaced by the inertance of the exit channel 511.

In the case in which the thickness of the tube wall of the connectionchannel tube 200 is large, the inertance L2 is obtained as the combinedinertance of the exit channel 511, the connection channel 201, and thenozzle 211.

Further, in the present embodiment, the channel length and the crosssection of the entrance channel 503 and the channel length and the crosssection of the exit channel 511 are set so that the inertance L1 on theentrance channel side becomes larger than the inertance L2 on the exitchannel side.

Hereinafter, a detailed configuration of the drive section 30 will beexplained with reference to FIGS. 5 through 7.

Here, FIG. 5 is a block diagram showing a detailed configuration of thedrive section 30. Further, FIG. 6 is a flowchart showing a process ofgenerating a signal waveform in the drive section 30. Still further,FIG. 7 is a flowchart showing a process of supplying the pulsationgeneration section 100 with a drive signal in the drive section 30.

As shown in FIG. 5, the drive section 30 is configured including anoperation control section 30 a, a signal waveform generation section 30b, a data storage section 30 c, a drive signal supply section 30 d, anda sync signal generation section 30 e.

The operation control section 30 a assumes the role of providing each ofthe constituents with an operational instruction in accordance with anoperational input from an input device (not shown) of the fluid jetdevice 1, and has a function of controlling various kinds of operationalprocesses such as a process of generating the signal waveform, or aprocess of supplying the drive signal.

The signal waveform generation section 30 b has a function of generatinga signal waveform with a shape suitable for driving the pulsationgeneration section 100 using the waveform information, a data table, andmeasurement data stored in the data storage section 30 c based on thejet emission intensity of the fluid jet emitting section 2, which is setbased on the input information of the user via the input device.

Specifically, as a signal waveform corresponding to one cycle of thedrive signal, there is generated a signal waveform configured includinga compressing drive waveform section for operating the piezoelectricelement 401 so as to compress the capacity of the fluid chamber 501, anda restoring drive waveform section for operating the piezoelectricelement 401 so as to restore the capacity of the fluid chamber 501,which is in the compressed state, to the state prior to the compression.

The signal waveform generation section 30 b of the present embodiment isarranged to generate the signal waveform composed of the compressingdrive waveform section and the restoring drive waveform sectionsatisfying the following formula 1.

Here, the time length of the compressing signal waveform section isdenoted as T_(red), and the time length of the restoring drive waveformsection is denoted as T_(exp). Further, average pressure in the fluidchamber 501 in a period of supplying the compressing drive waveformsection is denoted as P_(gen), and pressure applied to the entrancechannel 503 in the fluid chamber 501 on the pump 20 side in a period ofsupplying the restoring drive waveform section is denoted as P_(sup).T _(red)×(P _(gen) −P _(sup))≦T _(exp) ×P _(sup)  (1)

Hereinafter, the formula 1 described above will be explained.

When denoting the cross section of the entrance channel 503 as S, themomentum M_(g) acting on the entrance channel on the fluid chamber 501side is expressed as “M_(g)=S×T_(red)×(P_(gen)−P_(sup)).” On the otherhand, the momentum Ms acting on the entrance channel 503 on the pump 20side is expressed as “M_(s)=S×T_(exp)×P_(sup).” Further, in the fluidjet emitting section 2 with the configuration described above, it isknown that P_(sup) usually takes a value far smaller than P_(gen)(P_(gen)>>P_(sup)). Therefore, it is also possible to neglect P_(sup) inthe formula 1 described above.

Further, in a period (the period of T_(exp)) during which the capacityof the fluid chamber 501 is expanding (restoring the original capacity),the average pressure of the fluid chamber 501 becomes 0 atm or nearly 0atm (hereinafter, this pressure state is referred to as a vacuum state)because the fluid is drawn due to the inertance of the exit channel 511.

In other words, if the momentum M_(s) provided thereto in the period ofT_(exp) is equal to or larger than the momentum M_(g) provided theretoin the period of T_(red), the fluid can be restored to the originalsteady state.

Here, the steady state denotes the state in which the fluid flowsthrough the fluid chamber 501 while the supply pressure from the pump 20and the fluid resistance of the entire channel balance with each other.

Therefore, by supplying the piezoelectric element 401 forming thecapacity varying section with the drive signal having a signal waveform,which corresponds to one cycle thereof, and is composed of thecompressing drive waveform section with the time length T_(red) and therestoring drive waveform section with the time length T_(exp) satisfyingthe relationship of formula 1 described above, it is possible to restorethe fluid to the original steady state in a period corresponding to onecycle of the drive signal. Thus, it is possible to prevent thecompressing drive waveform section in the subsequent cycle from beingsupplied to the piezoelectric element 401 prior to returning to thesteady state, and therefore, the resulting degradation of the fluid jetforce can be prevented.

Further, by supplying the drive signal satisfying the formula 1described above, it is possible to gradually restore (expand) thecapacity of the fluid chamber 501 to the original state effectivelyusing the time necessary for restoring the flow rate in the entrancechannel 503. Thus, the expansion of the vacuum bubble is prevented, andthe gas emission to the vacuum bubble is reduced, and therefore, it ispossible to restore the steady state in the condition in whichsubstantially no gas bubble exists in the fluid chamber 501. Thus, itbecomes possible to reduce degradation of the fluid jet force caused bydegradation of the rigidity of the fluid chamber 501 due to the gasbubbles.

The signal waveform generation section 30 b of the present embodiment isfurther arranged to generate the signal waveform satisfying the formula1 described above using the waveform information of a plurality of typesof sine waves with periods different from each other stored in the datastorage section 30 c. Here, the waveform information is the data(digital data) obtained by sampling the signal levels (e.g., voltagevalues) of one cycle of the plurality of types of sine wave signals attime intervals Δt (shorter than one cycle).

Specifically, the signal waveform generation section 30 b of the presentembodiment is arranged to generate the signal waveform by combining thedata of a part of each of two sine wave signals with periods differentfrom each other. For example, it generates the signal waveform bysplicing the anterior half cycle (T1/2 (λ1/2)) of one sine wave and theposterior half cycle (T2/2 (λ2/2)) of the other sine wave with eachother.

It should be noted that regarding the waveform information of the sinewaves, it is possible to store one or some pieces of basic information,and generate desired waveform information by executing arithmeticprocessing on the basic information.

The signal waveform generation section 30 b of the present embodiment isused, for example, when performing the calibration of the waveforminformation upon powering on, or in replacing the fluid jet emittingsection 2.

Therefore, the signal waveform generation section 30 b has a function ofdetermining T_(red) and T_(exp) of the signal waveform corresponding tothe jet emission intensity set by the user based on the measurement datafrom a pressure sensor (not shown) capable of measuring the pressure ofthe fluid chamber 501, the entrance channel 503, and so on provided tothe fluid jet emitting section 2.

Specifically, when generating the signal waveform, the signal waveformgeneration section 30 b first determines T_(red) corresponding to thejet emission intensity set by the user and preliminary T_(exp) based ona data table stored in the data storage section 30 c, and then,generates the drive signal waveform based on T_(red) and preliminaryT_(exp). Subsequently, the signal waveform generation section 30 bdrives the pulsation generation section 100 (the piezoelectric element401) with the drive signal waveform, and measures P_(gen) and P_(sup) atthat moment based on the detection data of the pressure sensor. Further,the signal waveform generation section 30 b adjusts T_(exp) so thatP_(gen) and P_(sup) thus measured satisfy the formula 1 described above.The signal waveform generation section 30 b thereafter repeatedlyperforms generation of the drive signal waveform based on T_(red) thusdetermined and T_(exp) thus adjusted, driving of the pulsationgeneration section 100 with the signal waveform thus generated, andadjustment of T_(exp) until P_(gen) and P_(sup) thus measured satisfythe relationship of the formula 1 described above.

Further, the data storage section 30 c is configured including a storagemedium for storing waveform information described above related to aplurality of types of sine waves with periods and amplitudes differentfrom each other, the data table for determining T_(red) and T_(exp)corresponding to the jet emission intensity thus set, and other dataused for processing of respective constituents, and has a function ofreading out the data stored in the storage medium in response to a readrequest from each of the constituents and writing the data in thestorage medium in response to a write request from each of theconstituents. In other words, in addition to the function as thewaveform information storage section, the data storage section 30 c alsohas a function of storing other necessary data.

The drive signal supply section 30 d has a function of supplying thedrive signal to the piezoelectric element 401 of the capacity varyingsection forming the pulsation generation section 100 in sync with thesync signal from the sync signal generation section 30 e in response toa drive signal supply command from the operation control section 30 a.

Specifically, based on waveform designation information included in thesupply command, the drive signal supply section 30 d reads out thecorresponding waveform information (digital waveform data) from the datastorage section 30 c, executes DA conversion on the waveform informationthus read out to generate an analog drive signal, and supplies thepiezoelectric element 401 with the drive signal thus generated in syncwith the sync signal. It should be noted that the waveform designationinformation corresponds, for example, to identification informationattached to the signal waveform generated in the signal waveformgeneration section 30 b described above.

Further, it is arranged that when a halt command is input from theoperation control section 30 a in the process of supplying the drivesignal, the supply of the drive signal is halted after the entirewaveform of one cycle in the midstream of the supply process has beensupplied to the piezoelectric element 401.

The sync signal generation section 30 e includes an oscillator such as aceramic oscillator or a crystal oscillator, a counter (or a PLLcircuit), and so on, and has a function of generating the sync signalbased on a reference clock signal clk, which is a signal output from theoscillator. Further, the sync signal generation section 30 e suppliesthe drive signal supply section 30 d with the reference clock signal andthe sync signal.

It should be noted that the drive section 30 is provided with a computersystem for realizing the functions of the respective constituentsdescribed above with software, and for executing the software forcontrolling the hardware necessary for realizing the functions describedabove. Although the hardware configuration of the computer system is notshown in the drawings, there is adopted a configuration including aprocessor, a random access memory (RAM), and a read only memory (ROM),and connecting these elements with various internal and external buses.

Further, a display device such as a CRT or LCD monitor, and an inputdevice such as an operation panel, a mouse, or a keyboard are coupled tothe bus via an input/output interface (I/F) such as IEEE1394, USB, or aparallel port.

Further, it is arranged that when powering on, a system program storedin the ROM and so on loads various dedicated computer programs on theRAM, which are previously stored in the ROM, and for realizing thefunctions of the respective sections, and the processor fully usesvarious resources along the instructions described in the program loadedon the RAM to perform predetermined controls and arithmetic processing,thereby realizing the functions described above on the software.

Then, with reference to FIG. 6, the flow of the signal waveformgeneration process in the signal waveform generation section 30 b willbe explained.

When the processor executes the dedicated program to start the signalgeneration process, the process first proceeds to the step S100 as shownin FIG. 6.

In the step S100, whether or not a generation command of the signalwaveform from the operation control section 30 a is input is determinedin the signal waveform generation section 30 b, and if it is determinedthat the command is input (Yes), the process proceeds to the step S102,and otherwise (No) the determination process is repeated until thecommand is input.

In the case of proceeding to the step S102, the signal waveformgeneration section 30 b displays a setting screen for fluid jet emissionintensity, and then the process proceeds to the step S104.

In the step S104, whether or not the jet emission intensity is set bythe user via the input device is determined in the signal waveformgeneration section 30 b, and if it is determined that the intensity isset (Yes), the process proceeds to the step S106, and otherwise (No) thedetermination process is repeated until the intensity is set.

In the case of proceeding to the step S106, the signal waveformgeneration section 30 b determines T_(red) corresponding to the jetemission intensity set in the step S104 based on the data table, inwhich the time length T_(red) of the compressing signal waveform sectioncorresponding to a predetermined jet emission intensity is registered,and which is stored in the data storage section 30 c, and then theprocess proceeds to the step S108.

In the step S108, the signal waveform generation section 30 b determinespreliminary T_(exp) corresponding to the jet emission intensity set inthe step S104 based on the data table, in which the time length T_(exp)of the restoring signal waveform section corresponding to apredetermined type of jet emission intensity is registered, and which isstored in the data storage section 30 c, and then the process proceedsto the step S110.

In the step S110, the signal waveform generation section 30 b reads outtwo types of waveform information corresponding respectively to T_(red)determined in the step S106 and T_(exp) preliminarily determined in thestep S108 among a plurality of types of sinusoidal waveform informationstored in the data storage section 30 c, and then the process proceedsto the step S112.

In the step S112, the signal waveform generation section 30 b combinesthe anterior half cycle of one of the signal waveforms generated basedon the two types of waveform information read out in the step S110 andthe posterior half cycle of the other thereof to generate one cycle ofsignal waveform, and then the process proceeds to the step S114.

In the step S114, the signal waveform generation section 30 b outputs,to the operation control section 30 a, a drive request for making thedrive signal supply section 30 d drive the pulsation generation section100 with the signal waveform generated in the step S112, and then theprocess proceeds to the step S116.

In the step S116, the drive signal supply section 30 d outputs the drivesignal obtained by DA-converting the digital waveform signal (thewaveform information) generated in the step S112 into the analogwaveform signal to the piezoelectric element 401 of the pulsationgeneration section 100 in sync with the sync signal from the sync signalgeneration section 30 e in response to the drive command from theoperation control section 30 a, and then the process proceeds to thestep S118.

In the step S118, the signal waveform generation section 30 b measuresthe average pressure P_(gen) in the fluid chamber 501 during the supplyperiod of the compressing drive waveform section and the pressureP_(sup) applied to the entrance channel 503 in the fluid chamber 501 onthe pump 20 side during the supply period of the restoring drivewaveform section based on the detection data from the pressure sensorprovided to the fluid jet emitting section 2 in response to the supplyof the drive signal to the piezoelectric element 401 in the step S116,and then the process proceeds to the step S120.

In the step S120, the signal waveform generation section 30 b determineswhether or not P_(gen) and P_(sup) measured in the step S118, andT_(red) and T_(exp) thus determined satisfy the relationship of theformula 1 described above, and if it is determined that the relationshipis satisfied (Yes), the process proceeds to the step S122, and otherwise(No) the process proceeds to the step S128.

In the case of proceeding to the step S122, the signal waveformgeneration section 30 b stores the waveform information of the signalwaveform generated in the step S112 in the data storage section 30 c incorrespondence with the identification information unique to thewaveform information, and then the process proceeds to the step S124.

In the step S124, the signal waveform generation section 30 b outputs adrive halt request to the operation control section 30 a, and then theprocess proceeds to the step S126.

In the step S126, the drive signal supply section 30 d stops the supplyof the drive signal after outputting the entire signal waveformcorresponding to one cycle, and the series of process is terminated.

On the other hand, in the case in which the condition is not satisfied,and the process proceeds to the step S128 in the step S120, the signalwaveform generation section 30 b adjusts T_(exp) so as to satisfy therelationship of the formula 1 described above, and then the processproceeds to the step S130.

In the step S130, the signal waveform generation section 30 b reads outtwo types of waveform information corresponding respectively to T_(red)determined in the step S106 and T_(exp) adjusted in the step S122 amonga plurality of types of sinusoidal waveform information stored in thedata storage section 30 c, and then the process proceeds to the stepS112.

It should be noted that it is also possible to set the fluid jetemission intensity in the steps S102 and S104 by designating the rangecorresponding to the performance of the fluid jet emitting section 2. Onthis occasion, it should be arranged that the process of the steps S106through S124 is repeated for every jet emission intensity in the rangethus set.

Then, with reference to FIG. 7, the flow of the drive signal supplyprocess in the drive signal supply section 30 d will be explained.

When the processor executes the dedicated program to start the drivesignal supply process, the process first proceeds to the step S200 asshown in FIG. 7.

In the step S200, the drive signal supply section 30 d determineswhether or not a drive command from the operation control section 30 ais input, and if it is determined that the command is input (Yes), theprocess proceeds to the step S202, and otherwise (No) the processproceeds to the step S200.

In the case of proceeding to the step S202, the drive signal supplysection 30 d sets the waveform information of the waveform type used fordriving the fluid jet emitting section 2 based on the identificationinformation of the designated waveform included in the drive command,and then the process proceeds to the step S204.

In the step S204, the drive signal supply section 30 d reads out thewaveform information of the waveform type, which is set in the stepS202, from the data storage section 30 c, and then the process proceedsto the step S206.

In the step S206, the drive signal supply section 30 d outputs the drivesignal obtained by DA-converting the digital waveform signal thus readout into the analog waveform signal to the piezoelectric element 401 ofthe pulsation generation section 100 in sync with the sync signal fromthe sync signal generation section 30 e, and then the process proceedsto the step S208.

In the step S208, the drive signal supply section 30 d determineswhether or not a halt command is input from the operation controlsection 30 a, and if it is determined that the command is input (Yes),the process proceeds to the step S210, and otherwise (No) the outputprocess of the drive signal in the step S206 is continued.

In the case of proceeding to the step S210, the drive signal supplysection 30 d stops the supply of the drive signal after outputting theentire signal waveform corresponding to one cycle, and then the processproceeds to the step S212.

In the step S212, the drive signal supply section 30 d determineswhether or not a resume command is input from the operation controlsection 30 a, and if it is determined that the command is input (Yes),the process proceeds to the step S206 to resume the output process ofthe drive signal, and otherwise (No) the process proceeds to the stepS214.

In the case of proceeding to the step S214, whether or not a terminationcommand is input from the operation control section 30 a is determined,and if it is determined that the command is input (Yes), the drivesignal supply process is terminated, and otherwise (No) the processproceeds to the step S212.

Then, with reference to FIG. 8, a specific operation of the fluid jetdevice 1 of the present embodiment will be explained.

Here, FIG. 8 is a diagram showing an example of the signal waveformgenerated by combining two types of sine waves.

Firstly, a specific operation of the signal waveform generation processwill be explained.

When a calibration instruction of the signal waveform from the user isinput to the drive section 30 via the input device, the operationcontrol section 30 a outputs the generation command of the signalwaveform to the signal waveform generation section 30 b.

Meanwhile, when receiving the generation command of the signal waveform,the signal waveform generation section 30 b proceeds to the settingprocess of the fluid jet emission intensity (the branch of “Yes” in thestep S100).

The signal waveform generation section 30 b first displays (step S102)the setting screen of the fluid jet emission intensity desired by theuser on the display section not shown, thereby prompting the user to setthe jet emission intensity.

When the jet emission intensity is set (the branch of “Yes” in the stepS104) in accordance with the input information of the user via the inputdevice, the signal waveform generation section 30 b determines (stepS106) T_(red) (corresponding to the nearest value to the jet emissionintensity thus set) corresponding to the jet emission intensity thusset, based on the data table, which is stored in the data storagesection 30 c, and for determining T_(red).

Subsequently, the signal waveform generation section 30 b determines(step S108) preliminary T_(exp) (corresponding to the nearest value tothe jet emission intensity thus set) corresponding to the jet emissionintensity thus set based on the data table, which is stored in the datastorage section 30 c, and for preliminarily determining T_(exp).

When T_(red) and preliminary T_(exp) are determined, the signal waveformgeneration section 30 b then reads out the waveform information of theanterior half cycle of the sine wave sin 1 with a period nearest to thedouble (e.g., 0.2 [ms]) of T_(red) thus determined and the waveforminformation of the posterior half cycle of the sine wave sin 2 with aperiod nearest to the double of preliminary T_(exp) thus determined fromthe data storage section 30 c (step S110).

Then, the signal waveform generation section 30 b combines the two typesof waveform information thus read out, thereby generating the waveforminformation of the signal waveform with the compressing drive waveformsection having the time length of T_(red) determined as described above,and the restoring drive waveform section having the time length ofT_(exp) preliminarily determined as described above (step S112).

When the signal waveform is generated, the signal waveform generationsection 30 b outputs, to the operation control section 30 a, the driverequest for making the drive signal supply section 30 d drive thepiezoelectric element 401 of the pulsation generation section 100 withthe signal waveform thus generated (step S114).

Thus, the operation control section 30 a outputs, to the drive signalsupply section 30 d, the drive signal supply command for supplying thedrive signal of the signal waveform thus generated to the piezoelectricelement 401.

Meanwhile, when receiving the drive signal supply command of the signalwaveform thus generated as described above from the operation controlsection 30 a, the drive signal supply section 30 d executes the DAconversion on the waveform information included in the drive signalsupply command in sync with the sync signal from the sync signalgeneration section 30 e, and then outputs the analog signal obtained byexecuting the DA conversion to the piezoelectric element 401 of thepulsation generation section 100 as the drive signal (step S116).

When supply of the drive signal to the piezoelectric element 401 isstarted, the signal waveform generation section 30 b measures theaverage pressure P_(gen) in the fluid chamber 501 and the pressureP_(sup) applied to the entrance channel 503 in the fluid chamber 501 onthe pump 20 side, based on the detection data from the pressure sensorprovided to the fluid jet emitting section 2 (step S118).

Then, the signal waveform generation section 30 b determines whether ornot P_(gen) and P_(sup) thus measured satisfy the relationship of theformula 1 described above (step S120).

For example, it is assumed that P_(gen)=12 atm (1.2 MPa) and P_(sup)=2atm (0.2 MPa) are obtained based on the detection data of the pressuresensor.

On this occasion, according to the formula 1 described above,“0.1×(12−2)≦T_(exp)×2,” namely “0.5≦T_(exp)” is obtained. Therefore, ifT_(exp) is no larger than 0.5 [ms], it is determined that therelationship of the formula 1 described above is not satisfied (thebranch of “No” in the step S120).

For example, if present T_(exp) is 0.4 [ms], it is determined that therelationship of the formula 1 described above is not satisfied, and anadjustment such as adding 0.1 [ms] to present T_(exp) (0.4 [ms]) isexecuted (step S128). Further, the signal waveform generation section 30b reads out the waveform information corresponding to T_(red) thusdetermined and T_(exp) thus adjusted as described above from the datastorage section 30 c (step S130), and then the waveform information withadjusted T_(exp) is generated based on the waveform informationdescribed above (step S112).

Specifically, as illustrated by a heavy line in FIG. 8, there isgenerated a combined waveform obtained by connecting the maximum valueof the anterior half cycle (λ/2) of the sine wave sin 1 forming thecompressing drive waveform section Wc in one cycle of the signalwaveform, and the maximum value of the posterior half cycle (λ/2) of thesine wave sin 2 forming the restoring drive waveform section Wr therein.

The signal waveform generation section 30 b outputs a drive request tothe operation control section 30 a so as to drive the piezoelectricelement 401 with the signal waveform of the waveform information thusgenerated (step S114). Thus, the piezoelectric element 401 is drivenwith the signal waveform thus adjusted (step S116), and P_(gen) andP_(sup) are measured again based on the detection data of the pressuresensor (step S118).

Then, if P_(gen)=12 atm (1.2 MPa) and P_(sup)=2 atm (0.2 MPa) areobtained, since T_(red) has been set to be 0.1 [ms] and T_(exp) has beenset to be 0.5 [ms] in this case, it is determined that the relationshipof the formula 1 described above is satisfied (the branch of “Yes” inthe step S120).

When it is determined that T_(red) and T_(exp) satisfy the relationshipof the formula 1 described above, the signal waveform generation section30 b stores the waveform information of one cycle of the signal waveformcorresponding to these T_(red) and T_(exp) into the data storage section30 c in correspondence with the identification information (step S122).

It should be noted that on this occasion, it is also possible todetermine T_(exp) to be a value equal to or larger than 0.5 [ms] withrespect to T_(red) of 0.1 [ms].

Further, the waveform information is not limited to be of one cycle, butit is also possible to arrange that a plurality of cycles of waveforminformation is stored. In this case, in the waveforms each correspondingto one cycle and adjacent to each other, the lowest value of thecompressing drive waveform section of one of the waveforms and thelowest value of the restoring drive waveform section of the other of thewaveforms are connected to each other.

When the waveform information satisfying the relationship of the formula1 is stored, the signal waveform generation section 30 b outputs, to theoperation control section 30 a, the drive halt request for stopping thepiezoelectric element 401 in operation (step S124).

Thus, the operation control section 30 a outputs, to the drive signalsupply section 30 d, a drive signal supply halt command for stopping thesupply of the drive signal to the piezoelectric element 401.

Meanwhile, when receiving the drive signal supply halt command from theoperation control section 30 a, the drive signal supply section 30 dstops supplying the drive signal after outputting one whole cycle of thesignal waveform.

Then, a specific operation of the drive signal supply process will beexplained.

When the user holds down a drive switch (not shown), and the drivesignal supply instruction is input to the drive section 30, theoperation control section 30 a outputs the drive signal supply commandto the drive signal supply section 30 d.

Meanwhile, when receiving the drive signal supply command, the drivesignal supply section 30 d proceeds to the waveform information settingprocess (the branch of “Yes” in the step S200).

Since the drive signal supply command includes designated waveforminformation including the identification information of the waveforminformation used as the drive signal, the drive signal supply section 30d sets the waveform information with the identification informationcorresponding to the designated waveform information as the waveforminformation used for driving (step S202). Here, it is assumed that thewaveform information of the signal waveform illustrated by the heavyline shown in FIG. 8 and generated as described above is set.

When the waveform information used as the drive signal is set, the drivesignal supply section 30 d subsequently reads the waveform informationcorresponding to the waveform information thus set out from the datastorage section 30 c on a working memory such as the RAM (step S204).Subsequently, the drive signal supply section 30 d executes the DAconversion on the waveform information thus read out on the workingmemory in sync with the sync signal from the sync signal generationsection 30 e, and outputs the analog signal, which is thus converted inthe DA conversion, to the piezoelectric element 401 of the pulsationgeneration section 100 as the drive signal (step S206).

Before the drive signal is supplied, the pump 20 always supplies theentrance channel 503 with the fluid at constant fluid pressure. As aresult, when the piezoelectric element 401 does not operate, the fluidflows into the fluid chamber 501 due to the difference between theejection force of the pump 20 and the fluid resistance value of theentire channel on the entrance channel side.

Here, if the drive signal is input to the piezoelectric element 401 andthe piezoelectric element 401 rapidly expands in the period of T_(red)(0.1 [ms]), the pressure inside the fluid channel 501 rises rapidly upto several tens of atm, providing the inertances L1, L2 on the entrancechannel side and the exit channel side have sufficiently large values.

Since the pressure is far stronger than the pressure applied by the pump20 to the entrance channel 503, the inflow of the fluid from theentrance channel side into the fluid chamber 501 is reduced by thepressure, and the outflow thereof from the exit channel 511 isincreased.

However, since the inertance L1 of the entrance channel 503 is largerthan the inertance L2 of the exit channel 511, and therefore, theincreased amount of the fluid ejected from the exit channel is largerthan the decreased amount of the amount of flow of the fluid inflowingin the fluid chamber 501 from the entrance channel 503, pulsed fluidejection, namely a pulsation flow occurs in the connection channel 201.The pressure pulsation in the ejection operation propagates in theconnection channel tube 200, and thus the fluid jet is emitted from thefluid jet opening section 212 of the nozzle 211 at the tip of theconnection channel tube 200.

Here, since the diameter of the fluid jet opening section 212 of thenozzle 211 is smaller than the diameter of the exit channel 511, thefluid jet is emitted as a further high-pressure, high-speed, and pulseddroplet.

Meanwhile, inside the fluid chamber 501, there is provided a vacuumstate immediately after the rise in pressure due to the interactionbetween decrease in the amount of the fluid inflowing from the entrancechannel 503 and increase in the amount of the fluid outflowing from theexit channel 511.

On the other hand, after the rise in pressure, in the period of T_(exp)(0.5 [ms]), the piezoelectric element 401 in the expanded state slowlyshrinks taking time five times as long as the time T_(red) (0.1 [ms]) inthe expanding process. Thus, since the expansion of the vacuum bubblesis prevented, the flow of the fluid restores the steady state prior tothe supply of the drive signal while preventing generation of gasesinside the fluid chamber 501.

It should be noted that due to the fact that the fluid chamber 501 has ashape like a solid of revolution and is provided with the entrancechannel 503 and the fact that the exit channel 511 is opened in thevicinity of the rotational axis of the shape like a solid of revolution,the swirling flow occurs in the fluid chamber 501, and the bubbles (thevacuum bubbles and the gas bubbles) included in the fluid areimmediately discharged from the exit channel 511 to the outside.

Therefore, by continuously supplying the piezoelectric element 401 withthe drive signal having the signal waveform illustrated by the heavyline shown in FIG. 8, it is possible to continuously emit jet of thepulsation flow from the nozzle 211 in the state of maintaining strongjet force.

Further, as illustrated by the waveform of a thin line shown in FIG. 8,the level of the drive current in the period of T_(exp) can besuppressed to a lower level compared to the level of the drive currentin the period of T_(red). Therefore, in the case in which a bridgecircuit or the like is used as the drive circuit for driving thepiezoelectric element 401, since a rated value of the maximum peakcurrent of a current emitting transistor (e.g., the transistor on thelow side) among the transistors used in the circuit can be suppressed toa lower level, the cost for the transistor can be reduced.

Further, since it is arranged that the signal waveform of one cycle ofdrive signal is generated as a combination of sine waves as illustratedby the waveform of the heavy line shown in FIG. 8, it is possible tosmoothly couple signal waveforms with periods different from each other,and to reduce the stress to the mechanism of the fluid jet emittingsection 2.

Further, since the signal waveform generation section 30 b is capable ofgenerating the waveform information of the appropriate signal waveformin accordance with the values of P_(gen) and P_(sup) of the fluid jetemitting section 2, it is possible to easily perform replacement with afluid jet emitting section with different P_(gen) and P_(sup).

Second Embodiment

Hereinafter, a second embodiment of the invention will be explained withreference to the accompanying drawings. FIGS. 9A and 9B are diagramsshowing a fluid jet device, a drive device of the fluid jet device, asurgical instrument, and a method of driving the fluid jet deviceaccording to the second embodiment of the invention.

In comparison with the first embodiment described above, the presentembodiment is different therefrom in a part of the method of forming thesignal waveform satisfying the relationship of the formula 1 in thesignal waveform generation section 30 b of the drive section 30.Therefore, since the other part of the configuration is substantiallythe same as in the drive section 30 of the first embodiment describedabove, hereinafter the different part will be explained in detail, andthe explanations of the duplicated part will be omitted if appropriate.

The signal waveform generation section 30 b of the present embodiment isarranged to generate the signal waveform having a waveform sectiondisposed between the compressing drive waveform section and therestoring drive waveform section by expanding a part of the restoringdrive waveform section, the waveform section having an output level fordriving the piezoelectric element 401 so as to keep (stop the capacityvariation) the capacity of the fluid chamber 501 after the fluid chamber501 is compressed.

Here, FIG. 9A is a diagram showing an example of a method of expandingthe waveform, and FIG. 9B is a diagram showing an example of a signalwaveform of a drive signal according to the present embodiment.

Specifically, the signal waveform generation section 30 b generates thesignal waveform of the waveform shape as shown in FIG. 9B having theanterior half cycle t1 of the sine wave signal shown in FIG. 9A as thecompressing drive waveform section with the time length T_(red)(t1=T_(red)) satisfying the relationship of the formula 1 describedabove, a waveform section including an extension section obtained byextending the period with the maximum value in the posterior half cyclet2 (t1=t2) of the same sine wave signal so as to be the period ofT_(exp) satisfying the relationship of the formula 1 described above asthe restoring drive waveform section.

In other words, since the expansion of the vacuum bubble becomes apt tooccur by the rapid expansion of the capacity of the fluid chamber 501due to a rapid shrinkage operation subsequent to the expansion operation(capacity compression operation) of the piezoelectric element 401, bykeeping the expanded state of the piezoelectric element after thecapacity compression operation, it is possible to prevent the expansionof the vacuum bubbles and generation of the gas bubbles. Further, sinceit leads to waiting for the vacuum bubbles to disappear in thecompressed state, it is possible to make the vacuum bubbles disappear ina shorter period of time than in the first embodiment described above,and therefore, it is possible to restore the steady state in a shorterperiod of time than in the first embodiment described above.

The flow of the signal waveform generation process of the presentembodiment will hereinafter be explained.

The signal waveform generation process of the present embodiment isdifferent from that of the first embodiment described above only in theprocess content of the steps S110, S112, and S130 in the flowchart shownin FIG. 6, and the same in the process of the other steps.

Hereinafter, the process of the steps S110 and S112 of the presentembodiment will be explained.

In the step S110, the signal waveform generation section 30 b reads outthe waveform information corresponding to T_(red) determined in the stepS106 among a plurality of types of sinusoidal waveform informationstored in the data storage section 30 c, and then the process proceedsto the step S112.

In the step S112, the signal waveform generation section 30 b generatesthe signal waveform obtained by extending the posterior half cycle ofthe waveform information read out in the step S110 based on T_(exp) thuspreliminarily determined in the step S108, and the process proceeds tothe step S114.

It should be noted that in the step S130 the signal waveform obtained byextending the posterior half cycle of the waveform informationcorresponding to T_(red) based on T_(exp) thus adjusted.

Here, if the waveform information corresponding to T_(red) does notexist, the nearest one is read out, and then corrected for use therein.

Then, with reference to FIGS. 9A and 9B, a specific operation of thefluid jet device 1 of the present embodiment will be explained.

Firstly, a specific operation of the signal waveform generation processwill be explained.

Since the determination process of T_(red) and the preliminarydetermination process of T_(exp) are the same as in the first embodimentdescribed above, the process subsequent to the determination will beexplained.

When T_(red) and preliminary T_(exp) are determined, the signal waveformgeneration section 30 b then reads out the waveform information of theanterior half cycle of the sine wave sin 1 having one cycle the nearestto the double (e.g., 0.2 [ms]) of T_(red) thus determined from the datastorage section 30 c (step S110).

Subsequently, the signal waveform generation section 30 b generates thewaveform information of the signal waveform obtained by extending theperiod with the maximum value in the posterior half cycle in thewaveform information thus read out so that the posterior half cyclebecomes to have a period equal to or longer than at least T_(exp) thuspreliminarily determined (step S112).

Since the subsequent process (steps S114 through S120, and S128) issubstantially the same as in the first embodiment, the process afteradjusting T_(exp) in the step S128 will be explained.

After adjusting T_(exp), the signal waveform generation section 30 breads out the waveform information of a trapezoidal wave correspondingto the cycle double of T_(red) thus determined as described above fromthe data storage section 30 c (step S130), and corrects the waveforminformation thus read out so that the time length between nodal points Cand E of the waveform information becomes T_(exp) thus adjusted, therebygenerating the waveform information after T_(exp) is adjusted (stepS112).

Then, the signal waveform generation section 30 b outputs the driverequest (step S114) to make the drive signal supply section 30 d drivethe piezoelectric element 401 with the signal waveform of the waveforminformation thus generated (step S116).

When the drive signal is supplied to the piezoelectric element 401, thesignal waveform generation section 30 b measures P_(gen) and P_(sup)(step S118), and determines whether or not the measurement results,T_(red), and T_(exp) thus adjusted satisfy the relationship of theformula 1 described above (step S120).

In the determination, if the waveform information with T_(exp) adjustedsatisfies the relationship of the formula 1 described above (the branchof “Yes” in the step S120), the signal waveform generation section 30 bstores the waveform information into the data storage section 30 c incorrespondence with the identification number (step S122). Thesubsequent process of the steps S124 and S126 is substantially the sameas in the first embodiment, and therefore the explanations therefor willbe omitted.

When T_(exp) is adjusted so as to satisfy the relationship of theformula 1 described above, the signal waveform generation section 30 breads out the waveform information corresponding to T_(red) thusdetermined as described above from the data storage section 30 c (stepS130), and extends the posterior half cycle of the waveform information,thus read out, based on T_(exp) thus adjusted, thereby generating thewaveform information with T_(exp) adjusted (step S112).

Specifically, as shown in FIG. 9B, the signal waveform generationsection 30 b generates the signal waveform with the waveform shape inwhich the period with the maximum value of the restoring drive waveformsection continues for about 0.4 [ms].

The waveform information of the signal waveform corresponding to onecycle thus generated is stored in the data storage section 30 c incorrespondence with the identification number (step S122). It should benoted that the waveform information is not limited to be of one cycle,but it is also possible to arrange that a plurality of cycles ofwaveform information is stored. In this case, in the waveforms eachcorresponding to one cycle and adjacent to each other, the lowest valueof the compressing drive waveform section of one of the waveforms andthe lowest value of the restoring drive waveform section of the other ofthe waveforms are connected to each other.

The operation of the drive signal supply process is substantially thesame as in the first embodiment described above, and therefore theexplanations therefor will be omitted.

As described above, by supplying the drive signal with the signalwaveform shown in FIG. 9B thus generated as described above to thepiezoelectric element 401 of the pulsation generation section 100 tokeep the expanded state of the piezoelectric element after rapidlyexpanding the piezoelectric element to compress the capacity of thefluid chamber 501 in the period of the compressing drive waveformsection for 0.1 [ms], it is possible to prevent the expansion of thevacuum bubbles, and consequently generation of the gas bubbles.

Third Embodiment

Hereinafter, a third embodiment of the invention will be explained withreference to the accompanying drawings. FIGS. 10 through 14 are diagramsshowing a fluid jet device, a drive device of the fluid jet device, asurgical instrument, and a method of driving the fluid jet deviceaccording to the third embodiment of the invention.

In comparison with the first and second embodiments, the presentembodiment is different therefrom in the content of the waveforminformation stored in the data storage section 30 c of the drive section30, a part of the method of generating the signal waveform satisfyingthe relationship of the formula 1 described above in the signal waveformgeneration section 30 b of the drive section 30, and the method ofsupplying the drive signal in the drive signal supply section 30 d ofthe drive section 30. Therefore, since the other part of theconfiguration is substantially the same as in the drive section 30 ofthe first and second embodiments described above, hereinafter thedifferent part will be explained in detail, and the explanations of theduplicated part will be omitted if appropriate.

The signal waveform generation section 30 b of the present embodimenthas a function of generating a signal waveform to be a trapezoidal wavewith a shape suitable for determining T_(red) and T_(exp) satisfying therelationship of the formula 1 described above using the waveforminformation of the trapezoidal wave, a data table, and measurement datastored in the data storage section 30 c based on the jet emissionintensity of the fluid jet emitting section 2, which is set based on theinput information of the user via the input device, and driving thepulsation generation section 100.

Specifically, similarly to the case of the first embodiment, the signalwaveform generation section 30 b generates the signal waveform of thetrapezoidal wave having the compressing drive waveform section of thetime length T_(red) and the restoring drive waveform section of the timelength T_(exp) satisfying the relationship of the formula 1 describedabove. Then, the signal waveform generation section 30 b stores thenodal information of the trapezoidal wave thus generated into the datastorage section 30 c as the waveform information.

The data storage section 30 c of the present embodiment is configuredincluding a storage medium for storing the nodal information (time,voltage levels) of one cycle of a plurality of types of trapezoidalwaves with periods and amplitudes different from each other as thewaveform information, and in addition, other data used for processing ofrespective constituents, and has a function of reading out the datastored in the storage medium in response to a read request from each ofthe constituents and writing the data in the storage medium in responseto a write request from each of the constituents.

Then, with reference to FIG. 10, a detailed configuration of the drivesignal supply section 30 d of the present embodiment will be explained.

Here, FIG. 10 is a block diagram showing the detailed configuration ofthe drive signal supply section 30 d according to the presentembodiment.

As shown in FIG. 10, the drive signal supply section 30 d of the presentembodiment has a configuration including an interpolation section 31, acounter 33, and an amplifier 35.

The interpolation section 31 has a function of reading out the nodalinformation of the trapezoidal wave used as the drive signal from thedata storage section 30 c in response to the drive signal supply commandfrom the operation control section 30 a, and then setting an operatingcondition of the counter 33 for supplying the pulsation generationsection 100 with the drive signal based on the nodal information.

Here, FIG. 11 is a diagram showing an example of the trapezoidal waveforming the drive signal.

The data storage section 30 c stores the voltage information and thetime information of each of the nodal points A through E of thetrapezoidal wave shown in FIG. 11 as the waveform information. Thewaveform information of the nodal points A through C forms thecompressing drive waveform section, and the waveform information of thenodal points C through E forms the restoring drive waveform section.Further, in the case in which the time information is the information ofthe absolute time, T_(red) is defined as the time period correspondingto the difference obtained by subtracting the absolute time of the nodalpoint A from the absolute time of the nodal point C, and T_(exp) isdefined as the time period corresponding to the difference obtained bysubtracting the absolute time of the nodal point C from the absolutetime of the nodal point E.

Further, the operating condition of the counter corresponds to acondition for interpolating the waveform data between the nodal pointsadjacent to each other with the resolution of the clock signal clk usingthe waveform information of each of the nodal points, and thenperforming the DA conversion from the information of each of the nodalpoints of the trapezoidal wave into the signal information of thecontinuous analog trapezoidal wave. Therefore, as the operatingcondition of the counter, an initial value of counting, the number oftimes (the time direction) of increase and decrease of counting, anamount (the voltage direction) of increase and decrease of counting, andso on are set.

The counter 33 has a function of performing counting operation of theclock signal clk from the sync signal generation section 30 e based onthe operating condition set by the interpolation section 31, and thenoutputting the signal of the count value corresponding to the operatingcondition to the amplifier 35.

The amplifier 35 has a function of amplifying the signal input from thecounter 33 to be in a level appropriate for driving the piezoelectricelement 401, and then outputting it to the piezoelectric element 401 ofthe pulsation generation section 100.

Then, with reference to FIG. 12, the flow of the drive signal supplyprocess in the drive signal supply section 30 d of the presentembodiment will be explained.

Here, FIG. 12 is a flowchart showing a process (corresponding to thesteps S204 and S206 of the first embodiment described above) ofoutputting the drive signal in the drive signal supply process of thepresent embodiment.

When the drive signal output process is started, as shown in FIG. 12,the process firstly proceeds to the step S300.

In the step S300, the interpolation section 31 sets a start address ofthe waveform information, which is set as the drive signal, in a datalook-up address A, and then the process proceeds to the step S302.

In the step S302, the interpolation section 31 reads the time data “read(A, 1)” at the address A into a variable T(1), and then the processproceeds to the step S304.

Thus, “T(1)=read (A, 1)” is obtained.

In the step S304, the interpolation section 31 reads the waveform data“read (A, 2)” at the address A into a variable D(1), and then theprocess proceeds to the step S306.

Thus, “D(1)=read (A, 2)” is obtained.

In the step S306, the interpolation section 31 sets the value of D(1),which is read in the step S304, in a variable cnt as the initial valueof the counter, and then the process proceeds to the step S308.

Thus, “cnt=D(1)=read (A, 2)” is obtained.

In the step S308, the interpolation section 31 executes a countercondition setting process described later to set the counter condition,and then the process proceeds to the step S310.

In the step S310, the interpolation section 31 determines whether or notthe sync signal is detected, and if it is determined that the syncsignal is detected (Yes), the process proceeds to the step S312, andotherwise (No) the determination process is repeated until the syncsignal is detected.

If the process proceeds to the step S312, the interpolation section 31sets “0” in a variable k, and then the process proceeds to the stepS314. Here, the variable k is a variable for counting the number oftimes of the counting by the counter.

In the step S314, the counter 33 determines whether or not the value ofthe variable k is smaller than the value of a variable N, and if it isdetermined that it is smaller (Yes), the process proceeds to the stepS316, and otherwise (No) the process proceeds to the step S322. Here,the variable N is a variable in which the number of times of thecounting in the time axis necessary for moving from a certain nodalpoint to the next nodal point is set, and is set in the countercondition setting process described later.

If the process proceeds to the step S316, the counter 33 outputs thesignal waveform to the amplifier 35, and then the process proceeds tothe step S318.

In the step S318, the interpolation section 31 adds the value of avariable S to the present value of the variable cnt, and then theprocess proceeds to the step S320. Here, the variable S is a variable inwhich the amount of increase and decrease of the counting in the voltageaxis in each counting operation in a period from a certain nodal pointto the next nodal point is set, and is set in the counter conditionsetting process described later. If the value of the variable S is apositive number, the counter 33 counts up the value of the variable S,and if the value of the variable S is a negative number, the counter 33counts down the absolute value of the variable S.

In the step S320, the interpolation section 31 adds 1 to the presentvalue of the variable k, and then the process proceeds to the step S314.

On the other hand, if the value of the variable k exceeds the value ofthe variable N in the step S314, and the process proceeds to the stepS322, the interpolation section 31 determines whether or not the nextnodal point data exists, and if it is determined that it exists (Yes),the process proceeds to the step S324, and otherwise (No) the series ofprocess is terminated, and the process returns to the original process.

If the process proceeds to the step S324, the interpolation section 31executes the counter condition setting process to set the countercondition, and then the process proceeds to the step S312.

Then, with reference to FIG. 13, the flow of the counter conditionsetting process in the steps S308, S324 will be explained.

Here, FIG. 13 is a flowchart showing the counter condition settingprocess corresponding to the steps S308 and S324.

When the process proceeds to the step S308 or the step S324 and thecounter condition setting process is started, the process firstlyproceeds to the step S400 as shown in FIG. 13.

In the step S400, the interpolation section 31 adds 1 to the value ofthe data look-up address A, and then the process proceeds to the stepS402.

In the step S402, the interpolation section 31 reads the time data atthe address A into a variable T(2), and then the process proceeds to thestep S404.

Thus, “T(2)=read (A, 1)” is obtained.

In the step S404, the interpolation section 31 reads the waveform dataat the address A into a variable D(2), and then the process proceeds tothe step S406.

Thus, “D(2)=read (A, 2)” is obtained.

In the step S406, the interpolation section 31 substitutes the valueobtained by dividing the value, which is obtained by subtracting thevalue of the variable T(1) from the value of the variable T(2), by thetime (t_clk) of one cycle of the clock signal clk for the variable N asthe number of times of counting in the time axis necessary for reachingthe next nodal point, and then the process proceeds to the step S408.

In the step S408, the interpolation section 31 subtracts the value ofthe variable D(1) from the value of the variable D(2), and substitutesthe value obtained by dividing the result of the subtraction by thevalue of the variable N for the variable S as the amount of increase anddecrease of the counting in the voltage axis in each counting operation,and then the process proceeds to the step S410.

In the step S 410, the interpolation section 31 substitutes the value ofthe variable T(2) for the variable T(1), and the value of the variableD(2) for the variable D(1), then the series of process is terminated,and the process returns to the original process.

Then, with reference to FIGS. 14 and 15, a specific operation of thefluid jet device 1 of the present embodiment will be explained.

Here, FIG. 14 is a diagram showing an example of the waveforminformation of the present embodiment. Further, FIG. 15 is a diagramshowing an output example of the drive signal of the trapezoidal wave.

Since the determination process of T_(red) and the preliminarydetermination process of T_(exp) are the same as in the first embodimentdescribed above, the process subsequent to the determination will beexplained.

When T_(red) and preliminary T_(exp) are determined, the signal waveformgeneration section 30 b then reads out the waveform information of thetrapezoidal wave having one cycle the nearest to the double (e.g., 0.2[ms]) of T_(red) thus determined from the data storage section 30 c(step S110).

Here, in the case in which the time length between the nodal points Aand E in the waveform information of the trapezoidal wave thus read outis different from T_(red) thus determined as described above, the timeinformation of the waveform information thus read out is corrected.

Then, the time length between the nodal points C and E in the waveforminformation of the trapezoidal wave thus read out as described above iscorrected so as to be equal to or longer than T_(exp) thus preliminarilydetermined. In the manner as described above, by correcting the waveforminformation of a single type of trapezoidal wave, the waveforminformation of the trapezoidal signal waveform is generated (step S112).

It should be noted that as another method of generating the trapezoidalsignal waveform, there can be cited a method of generating the signalwaveform by combining the anterior half cycle of one of the waveforminformation of two types of trapezoidal waves with periods differentfrom each other with the posterior half cycle of the other thereof as inthe case of the first embodiment described above. Further, regarding thecorrection of the time length between the nodal points A and E,similarly to the case described above, there is cited a method ofperforming the correction by expending the time length between the nodalpoints C and D as in the second embodiment described above whencorrecting the time length between the nodal points C and E.

Since the subsequent process (steps S114 through S120, and S128) issubstantially the same as in the first embodiment, the process afteradjusting T_(exp) in the step S128 will be explained.

After adjusting T_(exp), the signal waveform generation section 30 breads out the waveform information of a trapezoidal wave correspondingto the cycle double of T_(red) thus determined as described above fromthe data storage section 30 c (step S130), and corrects the waveforminformation thus read out so that the time length between nodal points Cand E of the waveform information becomes T_(exp) thus adjusted, therebygenerating the waveform information after T_(exp) is adjusted (stepS112).

Then, the signal waveform generation section 30 b outputs the driverequest (step S114) to make the drive signal supply section 30 d drivethe piezoelectric element 401 with the signal waveform of the waveforminformation thus generated (step S116).

When the drive signal is supplied to the piezoelectric element 401, thesignal waveform generation section 30 b measures P_(gen) and P_(sup)(step S118), and determines whether or not the measurement results,T_(red), and T_(exp) thus adjusted satisfy the relationship of theformula 1 described above (step S120).

If the waveform information of one cycle of the signal waveform thusgenerated satisfies the relationship of the formula 1 described above(the branch of “Yes” in the step S120), the signal waveform generationsection 30 b stores the waveform information into the data storagesection 30 c in correspondence with the identification number (stepS122).

The operation of the drive signal supply process will hereinafter beexplained.

When the user holds down a drive switch (not shown), and the drivesignal supply instruction is input to the drive section 30, theoperation control section 30 a outputs the drive signal supply commandto the drive signal supply section 30 d.

Meanwhile, when receiving the drive signal supply command, the drivesignal supply section 30 d proceeds to the waveform information settingprocess (the branch of “Yes” in the step S200).

Since the drive signal supply command includes designated waveforminformation including the identification information of the waveforminformation used as the drive signal, the drive signal supply section 30d sets the waveform information with the identification informationcorresponding to the designated waveform information as the waveforminformation used for driving (step S202). Here, it is assumed that thewaveform information shown in FIG. 14 is set.

When the waveform information used as the drive signal is set, then theinterpolation section 31 sets the start address 101 in the data look-upaddress A (step S300), and subsequently reads the time data t0 at theaddress 101 into the variable T(1) (step S302). Thus, “T(1)=t0” isobtained.

Subsequently, the interpolation section 31 reads the waveform data P0 atthe address 101 into the variable D(1) (step S304). Thus, “D(1)=P0” isobtained.

Then, the interpolation section 31 sets the value P0 of the variableD(1) in the variable cnt as the initial value of the counter (stepS306), and the process proceeds to the counter condition setting process(step S308).

When the counter condition setting process is started, the interpolationsection 31 firstly adds 1 to the value of the data look-up address A(step S400). Thus, “A=102” is obtained.

Subsequently, the interpolation section 31 reads the time data t1 at theaddress 102 into the variable T(2) (step S402), and the waveform data P1at the address 102 into the variable D(2) (step S404). Thus, “T(2)=t1,D(2)=P1” is obtained.

Then, the interpolation section 31 subtracts the value t0 of thevariable T(1) from the value t1 of the variable T(2), calculates thenumber of times of the counting in the time axis by dividing the resultof the subtraction by the time (t_clk) of one cycle of the clock signalclk, and substitutes the calculation result “(t1−t0)/t_clk” for thevariable N. Thus, “N=(t1−t0)/t_clk” is obtained.

Subsequently, the interpolation section 31 subtracts the value P0 of thevariable D(1) from the value P1 of the variable D(2), calculates theamount of increase and decrease of the counter in the voltage axis bydividing the result of the subtraction by the number of times N of thecounting, and substitutes the calculation result “(P1−P0)/N” for thevariable S. Thus, “S=(P1−P0)/N” is obtained.

Lastly, the interpolation section 31 substitutes the value t1 of thevariable T(2) for the variable T(1), and the value P1 of the variableD(2) for the variable D(1), then the counter condition setting processis terminated, and the process returns to the original process (stepS410). Thus, “T(1)=t1,” “D(1)=P1” are obtained.

When the counter condition with respect to the counter 33 is set, thenthe interpolation section 31 waits for the sync signal from the syncsignal generation section 30 e to be detected, and if the sync signal isdetected (the branch of “Yes” in the step S310), the interpolationsection 31 initializes the variable k by setting “0” therein, andcompares the value “0” of the variable k with the value “(t1−t0)/t_clk”of the variable N to determine whether or not the value of the variablek is smaller than the value of the variable N (step S314).

Then, in the period in which the value of the variable k is smaller thanthe value of the variable N (the branch of “Yes” in the step S314), thesignal waveform with the voltage value determined by the value of thevariable cnt is output from the counter 33 to the amplifier 35 in everyclock (step S316), then the value of the variable S is added to thevalue of the variable cnt (step S318), and then 1 is added to the valueof the variable k (step S320).

Since in the example shown in FIG. 15 P0 and P1 are set to be “0 [V],”the amount S of increase and decrease of the counter becomes “0,” andtherefore, even if the value of the variable k increases, the value ofthe variable cnt is kept to the initial value of “0.” Therefore, thecounter 33 keeps outputting the signal waveform of “0 [V]” to theamplifier 35 while the value of the variable k is kept smaller than thevalue of the variable N.

Subsequently, when the value of the variable k exceeds the value of thevariable N (the brunch of “No” in the step S314), since the next nodalpoint data exists here (the branch of “Yes” in the step S322), theprocess proceeds to the counter condition setting process again (stepS324).

Similarly to the above, after executing the process of the steps S400through S410, “A=103,” “T(2)=t2,” “D(2)=P2,” “N=(t2−t1)/t_clk,”“S=(P2−P1)/N,” “T(1)=t2,” and “D(1)=P2” are obtained.

When the counter condition with respect to the counter 33 is set, thenthe interpolation section 31 waits for the sync signal from the syncsignal generation section 30 e to be detected, and if the sync signal isdetected (the branch of “Yes” in the step S310), the interpolationsection 31 initializes the variable k by setting “0” therein, andcompares the value “0” of the variable k with the value “(t2−t1)/t_clk”of the variable N to determine whether or not the value of the variablek is smaller than the value of the variable N (step S314).

Then, in the period in which the value of the variable k is smaller thanthe value of the variable N (the branch of “Yes” in the step S314), thesignal waveform with the voltage value determined by the value of thevariable cnt is output from the counter 33 to the amplifier 35 in everyclock (step S316), then the value of the variable S is added to thevalue of the variable cnt (step S318), and further 1 is added to thevalue of the variable k (step S320).

Since in the example shown in FIG. 15, P2 is set to be a “value (assumedto be 3 [V] here) larger than 0 [V],” the amount S of increase anddecrease of the counter becomes “(3/N)[V],” and the value of thevariable cnt increases by “(3/N) [V]” every time the value of thevariable k increases by 1. Therefore, the counter 33 outputs the signalwaveform, which increases by “(3/N) [V]” every time the value of thevariable k increases by “1,” to the amplifier 35.

Subsequently, when the value of the variable k exceeds the value of thevariable N (the brunch of “No” in the step S314), since the next nodalpoint data exists here (the branch of “Yes” in the step S322), theprocess proceeds to the counter condition setting process again (stepS324).

Similarly to the above, after executing the process of the steps S400through S410, “A=104,” “T(2)=t3,” “D(2)=P3,” “N=(t3−t2)/t_clk,”“S=(P3−P2)/N,” “T(1)=t3,” and “D(1)=P3” are obtained.

When the counter condition with respect to the counter 33 is set, thenthe interpolation section 31 waits for the sync signal from the syncsignal generation section 30 e to be detected, and if the sync signal isdetected (the branch of “Yes” in the step S310), the interpolationsection 31 initializes the variable k by setting “0” therein, andcompares the value “0” of the variable k with the value “(t3−t2)/t_clk”of the variable N to determine whether or not the value of the variablek is smaller than the value of the variable N (step S314).

Then, in the period in which the value of the variable k is smaller thanthe value of the variable N (the branch of “Yes” in the step S314), thesignal waveform with the voltage value determined by the value of thevariable cnt is output from the counter 33 to the amplifier 35 in everyclock (step S316), then the value of the variable S is added to thevalue of the variable cnt (step S318), and further 1 is added to thevalue of the variable k (step S320).

Since in the example shown in FIG. 15, P3 is set to be “the same value 3[V] as that of P2,” the amount S of increase and decrease of the counterbecomes “0 [V],” and therefore, even if the value of the variable kincreases, the value of the variable cnt is kept to “3 [V].” Therefore,the counter 33 keeps outputting the signal waveform of “3 [V]” to theamplifier 35 while the value of the variable k is kept smaller than thevalue of the variable N. Therefore, the counter 33 outputs the signalwaveform of “3 [V]” to the amplifier 35 every time the value of thevariable k increases by “1.”

Subsequently, when the value of the variable k exceeds the value of thevariable N (the brunch of “No” in the step S314), since the next nodalpoint data exists here (the branch of “Yes” in the step S322), theprocess proceeds to the counter condition setting process again (stepS324).

Similarly to the above, after executing the process of the steps S400through S410, “A=105,” “T(2)=t4,” “D(2)=P4,” “N=(t4−t3)/t_clk,”“S=(P4−P3)/N,” “T(1)=t4,” and “D(1)=P4” are obtained.

When the counter condition with respect to the counter 33 is set, thenthe interpolation section 31 waits for the sync signal from the syncsignal generation section 30 e to be detected, and if the sync signal isdetected (the branch of “Yes” in the step S310), the interpolationsection 31 initializes the variable k by setting “0” therein, andcompares the value “0” of the variable k with the value “(t4−t3)/t_clk”of the variable N to determine whether or not the value of the variablek is smaller than the value of the variable N (step S314).

Then, in the period in which the value of the variable k is smaller thanthe value of the variable N (the branch of “Yes” in the step S314), thesignal waveform with the voltage value determined by the value of thevariable cnt is output from the counter 33 to the amplifier 35 in everyclock (step S316), then the value of the variable S is added to thevalue of the variable cnt (step S318), and further 1 is added to thevalue of the variable k (step S320).

Since in the example shown in FIG. 15, P4 is set to be “0 [V],” and P3is set to be “3 [V],” the amount S of increase and decrease of thecounter becomes “(−3/N) [V],” and the value of the variable cntdecreases by “(3/N) [V]” from 3 [V] every time the value of the variablek increases by 1. Therefore, the counter 33 outputs the signal waveform,which decreases by “(3/N) [V]” from the previous value every time thevalue of the variable k increases by “1,” to the amplifier 35.

Subsequently, when the value of the variable k exceeds the value of thevariable N (the branch of “No” in the step S314), since the next nodalpoint data does not exist here (the branch of “No” in the step S322),the process proceeds to the original process, and if a halt command or atermination command is provided, the drive signal supply process ishalted or terminated. On the other hand, if neither the halt command northe termination command is provided, the process from the step S300 isexecuted again with respect to the waveform information thus set. Thus,the signal waveform of the same waveform information can continuously beoutput.

It should be noted that the operation of the fluid jet emitting section2 after supplying the piezoelectric element 401 with the drive signal issubstantially the same as the operation of the first embodimentdescribed above, and therefore, the explanations therefor will beomitted.

As explained hereinabove, if the nodal point data of the trapezoidalwave is stored in the data storage section 30 c, the fluid jet device 1of the present embodiment can supply the piezoelectric element 401 ofthe pulsation generation section 100 with the drive signal composed ofthe analog trapezoidal signal waveform while interpolating the databetween the nodal points using the nodal point data.

Thus, since the data capacity of the waveform information cansignificantly be reduced in comparison with the case of the sine waves,the memory device with a large capacity is not required, and the fluidjet device can be configured with relatively low cost.

Further, since it is arranged that the signal waveform output process isexecuted using the algorithms shown in the flow charts of the steps S208through S220 described above and the steps S300 through S324 describedabove, even if the drive signal supply command and the drive signal haltcommand are input at any timing, it is possible to supply thepiezoelectric element 401 with the drive signal so as to always startwith the head of the waveform and end with the tail thereof.

Thus, since it does not occur that the drive signal is supplied to thepiezoelectric element 401 from the middle of the waveform or that thedrive signal is suddenly switched to a no signal state in the middle ofthe supply of the drive signal, the piezoelectric element 401 can beprevented from being damaged by, for example, suddenly shrinking thepiezoelectric element 401.

It should be noted that although in the first embodiment theconfiguration capable of generating the waveform information with anappropriate signal waveform in accordance with the measurement values ofP_(gen) and P_(sup) of the fluid jet emitting section 2 is explained,the configuration is not limited thereto, but can be a configuration ofpreviously generating the waveform information of the signal waveformcorresponding to the values of P_(gen) and P_(sup), and holding thewaveform information. According to this configuration, although thedrive section 30 becomes only available for the fluid jet emittingsection 2 of the same pressure specification, since the pressure sensor,the signal waveform generation section 30 b, and so on becomeunnecessary to be provided, the corresponding cost (the cost of thesensor, the cost of writing the program, and so on) can be reduced.Further, as another embodiment, it is also possible to adopt aconfiguration in which the values of P_(gen) and P_(sup) measuredpreviously prior to the shipment are stored in the fluid jet emittingsection 2 (e.g., by adding a memory device storing the values), and thevalues of P_(gen) and P_(sup) are obtained when replacing the fluid jetemitting section 2 or powering on to generate the waveform informationof the signal waveform corresponding to the values of P_(gen) andP_(sup). According to this configuration, since it can cope with aplurality of types of pressure specifications, and need for providingthe pressure sensor for measuring P_(gen) and P_(sup) is eliminated, thecost can be reduced accordingly.

Further, although the first through third embodiments described above,which are preferable specific examples of the invention, are providedwith various technically preferable limitations, the scope of theinvention is not limited to these embodiments unless the description tolimit the invention thereto is particularly presented in theexplanations described above. Further, the drawings used in theexplanations described above are schematic diagrams having contractionscales in the vertical and horizontal directions of the members or partsdifferent from the actual scales for the sake of convenience ofillustration.

Further, the invention is not limited to the first through thirdembodiments described above but includes modifications and improvementswithin a range where the advantages of the invention can be achieved.

What is claimed is:
 1. A fluid jet device comprising: a fluid chamberwith a variable capacity; an entrance channel communicated with thefluid chamber; an exit channel communicated with the fluid chamber; acapacity varying section adapted to vary the capacity of the fluidchamber in response to supply of a drive signal; an opening sectioncommunicated with the exit channel; a pressure generation sectionadapted to supply the entrance channel with a fluid; and a drive signalsupply section adapted to supply the capacity varying section with adrive signal including a compressing drive waveform section making thecapacity varying section operate so as to compress the capacity of thefluid chamber and a restoring drive waveform section making the capacityvarying section operate so as to restore the capacity of the fluidchamber before compressing the capacity in a signal waveform of onecycle; and an operation controlling section adapted to control supplyingthe drive signal in response to input to an input section; wherein whena stopping instruction of the drive signal is issued from the operationcontrolling section while the drive signal is being supplied to thecapacity varying section, the drive signal supply section stopssupplying the drive signal after an entire waveform of one cycle issupplied to the capacity varying sections.
 2. The fluid jet deviceaccording to claim 1, wherein a time length of the compressing drivewaveform section is denoted as T_(red), a time length of the restoringdrive waveform section is denoted as T_(exp), average pressure in thefluid chamber in a supply period of the compressing drive waveformsection is denoted as P_(gen), pressure applied to the entrance channelin the fluid chamber on a pressure generation section side in a supplyperiod of the restoring drive waveform section is denoted as P_(sup),and the drive signal supply section supplies the capacity varyingsection with the drive signal configured including the compressing drivewaveform section with the time length T_(red) and the restoring drivewaveform section with the time length T_(exp) satisfying a relationshipof a following formula:T _(red)×(P _(gen) −P _(sup))≦T _(exp) ×P _(sup).
 3. The fluid jetdevice according to claim 1, wherein the drive signal supply sectioncontrols the supply content of the drive signal so as to provide therestoring period in the supply period of the restoring drive waveformsection.
 4. The fluid jet device according to claim 3, wherein the drivesignal supply section supplies the capacity varying section with thedrive signal having a constant waveform section between the compressingdrive waveform section and the restoring drive waveform section, theconstant waveform section forming a constant signal level in a part ofthe restoring drive waveform section, the constant signal levelcorresponding to the restoring period.
 5. The fluid jet device accordingto claim 1, wherein the drive signal supply section supplies thecapacity varying section with the drive signal having the signalwaveform of one cycle configured by combining a part of a sine wave,which forms the compressing drive waveform section, and a time length ofone cycle of which is T1, and a part of a sine wave, which forms therestoring drive waveform section, and a time length of one cycle ofwhich is T2 (T1<T2).
 6. The fluid jet device according to claim 1,wherein a shape of a trapezoidal wave is adopted as the signal waveformof one cycle.
 7. The fluid jet device according to claim 6, wherein thestorage section stores nodal point information of the trapezoidal waveas the waveform information, and the drive signal supply sectiongenerates the drive signal of the trapezoidal wave based on the nodalpoint information stored in the storage section.
 8. The fluid jet deviceaccording to claim 1, wherein a diameter of an end of the exit channelon a fluid chamber side is set to be larger than a diameter of an end ofthe exit channel on an opening section side.
 9. The fluid jet deviceaccording to claim 1, wherein an inertance of the entrance channel isset to be larger than an inertance of the exit channel.
 10. The fluidjet device according to claim 1, wherein a combined inertance on anupstream side of the fluid chamber including the entrance channel islarger than an inertance on a downstream of the fluid chamber includingthe exit channel.
 11. The fluid jet device according to claim 1, furthercomprising: a connection channel having a first end communicated withthe exit channel, and a second end provided with the opening sectionhaving a diameter smaller than a diameter of the exit channel; and aconnection channel tube through which the connection channel penetrates,and which transmits pulsation of the fluid flowing from the fluidchamber to the opening section.
 12. The fluid jet device according toclaim 1, wherein the capacity varying section includes: a diaphragmadapted to seal an end of the fluid chamber, and a piezoelectric elementhaving one end fixed to the diaphragm and one of expanding and shrinkingin a direction perpendicular to a seal surface in response to supply ofthe drive signal, and the drive signal supply section makes thepiezoelectric element expand to deform the diaphragm toward an inside ofthe fluid chamber by supplying the compressing drive waveform section inthe drive signal, and makes the piezoelectric element shrink to restorethe diaphragm in a deformed state to the diaphragm in a state prior tothe deformation by supplying the restoring drive waveform section in thedrive signal.
 13. A surgical instrument adapted to assist a therapeutictreatment of an affected area by fluid jet emission, comprising: the jetdevice according to claim 1.